My mother and I visit Hiroshima, Japan, March 19, 2016.

Hiroshima Prefecture is located in the southwestern part of the Japanese islands. It is rich in the natural beauty of the Inland Sea and the Chugoku Mountains, with mountains, sea, rivers, valleys, plains, basins that characterize Japan's landscape.

Hiroshima Castle (広島城, Hiroshimajō), also called the Carp Castle, is a good example of a castle built on a plain in the center of a city as opposed to hilltop and mountaintop castles. Its main keep is five stories tall, and its grounds are surrounded by a moat. Also within the castle's precincts are a shrine, some ruins and a few reconstructed buildings of the Ninomaru (second circle of defense).

Hiroshima developed as a castle town, whereby the castle was both the physical and economical center of the city. Built in 1589 by the powerful feudal lord Mori Terumoto, Hiroshima Castle was an important seat of power in Western Japan. While it was spared the demolishment that many other castles met during the Meiji Restoration, like the rest of the city, Hiroshima Castle was destroyed by the atomic bomb in 1945.

The A-Bomb Dome is a symbol of peace which most people have at least seen at one time in a picture. The building, which was designed by a Czech architect in 1915, had been used as the Hiroshima Prefectural Industrial Promotion Hall. Hiroshima citizens back then loved so much European modern-style buildings of the time. In 1912, the National Confectionery Exposition was held in this place. From that exposition, Baumkuchen, which represented German cake, was manufactured and sold in Japan for the first time. Since the Hiroshima Prefectural Industrial Promotion Hall was located only around 160 meters from the hypocenter, the building was blown up, and all those inside the building died. However, the building was not destroyed completely because the blast of the atomic bomb, which was vaporized in the air, prevented it from totally collapsing. It was designated a UNESCO World Heritage Site in 1996 and has been representing people's prayers for a lasting peace.

Photo by John L. Carkeet IV, LimpingFog Productions

This is a seismogram for the Maple Creek seismic station in Yellowstone, Wyoming. The noise on the 19:00 line (click on the image once or twice to zoom in) was caused by shock waves from a magnitude 6.3 earthquake that hit offshore from the Sandwich Islands in the far-southern Atlantic Ocean (it's actually in the Antarctic Ocean). The quake occurred at late 10:53 PM, local time, on 25 July 2020. Shock waves arrived at the seismic station at early 7:13 PM, Yellowstone time, ~19 minutes after the quake hit.

The epicenter occurred along a transform fault in the South Scotia Ridge, a mid-ocean ridge between the Antarctic Plate (to the south) and the Scotia Plate-South Sandwich Plate-South American Plate (to the north) (see: en.wikipedia.org/wiki/South_Sandwich_Trench#/media/File:E... ).

Mid-ocean ridges are seafloor mountain chains that form where tectonic divergence occurs - two tectonic plates move away from each other. These seafloor ridges are frequently offset by relatively short transform faults, resulting in a zig-zag pattern in map view. The South Scotia Ridge is unusual in having long transform faults offsetting individual ridge segments.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000b46r/exec...

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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This map shows a cluster of 114 earthquake events that occurred on the 10th and 11th of September 2020 south of Yellowstone Lake's West Thumb (= gray area at the top margin of the map). Quake magnitudes ranged from 0.1 to 2.8. Clusters of earthquakes are called "swarms".

Additional small earthquakes occurred in the area up to 16 September 2020, for a total of about 125 events.

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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This is a seismogram from the Gunungsitoli seismic station on Nias Island, Indonesia. The noise was caused by a magnitude 6.2 offshore earthquake in Indonesia. The quake hit at 5:29 AM, local time, on 16 January 2023. The epicenter was about 43 kilometers west of the town of Barus, Sumatra, Indonesia. The hypocenter was between 35 and 40 kilometers deep. Shaking resulted from thrust faulting along a northwest-southeast striking fault zone.

--------------------------------

Info. at:

earthquake.usgs.gov/earthquakes/eventpage/us7000j4kr/exec...

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

The noise on the 00:00 and 01:00 lines on this seismogram from the Monasavu station in the Fiji Islands represents shock waves from a magnitude 6.2 earthquake. It occurred in the New Hebrides Trench area, offshore from the islands of Vanuatu (= western Pacific Ocean). The quake hit at 11:49 AM, local time, on 16 February 2021. The epicenter was about 80 to 90 kilometers ~west of Efate Island.

This was a subduction zone earthquake. Subduction zones have tectonic plates composed of oceanic lithosphere diving underneath another tectonic plate. In this case, the Australian Plate is subducting eastward beneath the Pacific Plate along deep seafloor troughs called the New Hebrides Trench and North New Hebrides Trench.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000dhxn/exec...

and

earthquake.usgs.gov/earthquakes/eventpage/us6000dhxn/regi... [Scroll down for a tectonic summary of the area - see paragraphs 6, 7, and 8.]

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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This seismogram is from the Tristan da Cunha seismic station in the South Atlantic Ocean. The prominent noise on the 21:00 to 23:00 lines in the middle of the graph was caused by shock waves from a magnitude 7.1 earthquake that occurred in the South Sandwich Trench area (= far-southern Atlantic Ocean; it's actually just in the Antarctic Ocean). The quake hit at 7:33 PM, local time, on 22 August 2021. The epicenter was about 162 kilometers southeast of Cook Island. The hypocenter was about 14 kilometers deep. This event was a large aftershock of a magnitude 8.1 quake in the same area on 12 August 2021 (see: www.flickr.com/photos/jsjgeology/51374098706).

The South Sandwich Trench is a deep seafloor trough formed by subduction - oceanic lithosphere of the South American Plate is diving westward beneath oceanic lithosphere of the Sandwich Plate. Earthquake activity and volcanic islands occur next to the trench.

This quake occurred during a Moon-Earth-Sun alignment.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000f9sq/exec...

and

en.wikipedia.org/wiki/South_Sandwich_Trench

and

en.wikipedia.org/wiki/South_Sandwich_Plate

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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This seismogram is from the Casey seismic station in Antarctica. The noise was caused by a magnitude 6.3 offshore earthquake that occurred below the Indian Ocean seafloor. The quake hit at 3:25 AM, local time, on 5 February 2022.

This earthquake occurred along the Southeast Indian Ridge (SEIR), where the Indian-Australian Plate and the Antarctic Plate diverge (separate). Shaking resulted from right-lateral slip along a northeast-southwest striking fault zone. The fault is unnamed, but has been designated the SEIR 100E Transform Fault, in reference to its location at 100 degrees East longitude. Transform faults are common along mid-ocean ridges - they offset the spreading centers, resulting in a zig-zag pattern in map view.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us7000gi25/exec...

and

en.wikipedia.org/wiki/Southeast_Indian_Ridge

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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This is a seismogram from the Otavalo seismic station in Ecuador. The prominent noise was caused by shock waves from a magnitude 6.2 earthquake that hit northwestern Peru near the western coastline of South America. The quake occurred at 12:10 PM, local time, on 30 July 2021. The epicenter was south of the Chira River Valley, between the towns of Sullana and Tambo Grande in Piura Department, Peru. The hypocenter was between 30 and 35 kilometers deep.

Western South America consists of an extensive orogenic belt called the Andes Mountains - these formed principally by subduction, which involves one tectonic plate composed of oceanic lithosphere diving beneath another tectonic plate. In this case, the subducting slab is the eastward-moving Nazca Plate and the overriding slab is westward-moving South American Plate continental lithosphere. Frequent seismicity and active volcanism occur in the Andes as a result. The subduction zone itself is a deep seafloor trough called the Peru-Chile Trench.

If I'm reading the fault plane solution correctly, this earthquake occurred along a ~north-south striking, shallowly westward-dipping backthrust fault.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000f0qr/exec...

and

www.volcanodiscovery.com/earthquakes/6345558/2021-07-30/1...

and

en.wikipedia.org/wiki/Peru–Chile_Trench

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

The Genbaku Dōmu (A-bomb dome), as the Hiroshima Peace Memorial (Hiroshima heiwa kinenhi) is most commonly known, is the skeletal ruins of the former Hiroshima Prefectural Industrial Promotion Hall, designed by Czech architect Jan Letzel and constructed in 1915.

Being almost directly at the hypocenter, the A-Bomb Dome was one of the few structures at a 3km radius to remain, at least partially, standing. The wire framework of the dome and the walls standing have undergone several preservation projects and have become a symbol as a historical witness that conveys the disaster of the first atomic bombing in history. It was designated a UNESCO World Heritage Site in 1996.

My mother and I visit Hiroshima, Japan, March 19, 2016.

Hiroshima Prefecture is located in the southwestern part of the Japanese islands. It is rich in the natural beauty of the Inland Sea and the Chugoku Mountains, with mountains, sea, rivers, valleys, plains, basins that characterize Japan's landscape.

Hiroshima Castle (広島城, Hiroshimajō), also called the Carp Castle, is a good example of a castle built on a plain in the center of a city as opposed to hilltop and mountaintop castles. Its main keep is five stories tall, and its grounds are surrounded by a moat. Also within the castle's precincts are a shrine, some ruins and a few reconstructed buildings of the Ninomaru (second circle of defense).

Hiroshima developed as a castle town, whereby the castle was both the physical and economical center of the city. Built in 1589 by the powerful feudal lord Mori Terumoto, Hiroshima Castle was an important seat of power in Western Japan. While it was spared the demolishment that many other castles met during the Meiji Restoration, like the rest of the city, Hiroshima Castle was destroyed by the atomic bomb in 1945.

The A-Bomb Dome is a symbol of peace which most people have at least seen at one time in a picture. The building, which was designed by a Czech architect in 1915, had been used as the Hiroshima Prefectural Industrial Promotion Hall. Hiroshima citizens back then loved so much European modern-style buildings of the time. In 1912, the National Confectionery Exposition was held in this place. From that exposition, Baumkuchen, which represented German cake, was manufactured and sold in Japan for the first time. Since the Hiroshima Prefectural Industrial Promotion Hall was located only around 160 meters from the hypocenter, the building was blown up, and all those inside the building died. However, the building was not destroyed completely because the blast of the atomic bomb, which was vaporized in the air, prevented it from totally collapsing. It was designated a UNESCO World Heritage Site in 1996 and has been representing people's prayers for a lasting peace.

Photo by John L. Carkeet IV, LimpingFog Productions

This is a seismogram from the Port Moresby seismic station on New Guinea island. The prominent noise was caused by a magnitude 7.0 earthquake in Papua New Guinea. The quake hit at 4:04 AM, local time, on 3 April 2023. The epicenter was near the eastern shoreline of Chambri Lake in northern Papua New Guinea. The hypocenter was between 60 and 70 kilometers deep. This is the seventh magnitude 7+ earthquake of 2023.

--------------------------------

Info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000k1id/exec...

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This seismogram is from the Tristan da Cunha seismic station in the South Atlantic Ocean. The prominent noise on the 21:00 line at the bottom of the graph was caused by shock waves from a magnitude 7.1 earthquake that occurred in the South Sandwich Trench area (= far-southern Atlantic Ocean; it's actually just in the Antarctic Ocean). The quake hit at 7:33 PM, local time, on 22 August 2021. The epicenter was about 162 kilometers southeast of Cook Island. The hypocenter was about 14 kilometers deep. This event was a large aftershock of a magnitude 8.1 quake in the same area on 12 August 2021 (see: www.flickr.com/photos/jsjgeology/51374098706).

The South Sandwich Trench is a deep seafloor trough formed by subduction - oceanic lithosphere of the South American Plate is diving westward beneath oceanic lithosphere of the Sandwich Plate. Earthquake activity and volcanic islands occur next to the trench.

This quake occurred during a Moon-Earth-Sun alignment.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000f9sq/exec...

and

en.wikipedia.org/wiki/South_Sandwich_Trench

and

en.wikipedia.org/wiki/South_Sandwich_Plate

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

The Atomic Bomb Dome serves as a memorial to the people who died in the atomic bombing of Hiroshima, Japan, in 1945. The building was the only structure left standing near the bomb’s hypocenter. Photo by Barbara Dunlap-Berg, UMNS

My mother and I visit Hiroshima, Japan, March 19, 2016.

Hiroshima Prefecture is located in the southwestern part of the Japanese islands. It is rich in the natural beauty of the Inland Sea and the Chugoku Mountains, with mountains, sea, rivers, valleys, plains, basins that characterize Japan's landscape.

Hiroshima Castle (広島城, Hiroshimajō), also called the Carp Castle, is a good example of a castle built on a plain in the center of a city as opposed to hilltop and mountaintop castles. Its main keep is five stories tall, and its grounds are surrounded by a moat. Also within the castle's precincts are a shrine, some ruins and a few reconstructed buildings of the Ninomaru (second circle of defense).

Hiroshima developed as a castle town, whereby the castle was both the physical and economical center of the city. Built in 1589 by the powerful feudal lord Mori Terumoto, Hiroshima Castle was an important seat of power in Western Japan. While it was spared the demolishment that many other castles met during the Meiji Restoration, like the rest of the city, Hiroshima Castle was destroyed by the atomic bomb in 1945.

The A-Bomb Dome is a symbol of peace which most people have at least seen at one time in a picture. The building, which was designed by a Czech architect in 1915, had been used as the Hiroshima Prefectural Industrial Promotion Hall. Hiroshima citizens back then loved so much European modern-style buildings of the time. In 1912, the National Confectionery Exposition was held in this place. From that exposition, Baumkuchen, which represented German cake, was manufactured and sold in Japan for the first time. Since the Hiroshima Prefectural Industrial Promotion Hall was located only around 160 meters from the hypocenter, the building was blown up, and all those inside the building died. However, the building was not destroyed completely because the blast of the atomic bomb, which was vaporized in the air, prevented it from totally collapsing. It was designated a UNESCO World Heritage Site in 1996 and has been representing people's prayers for a lasting peace.

Photo by John L. Carkeet IV, LimpingFog Productions

The 6 August 1945 nuclear explosion was almost directly above this building (the hypocenter was 150 meters / 490 feet away), and it was the closest structure to withstand the explosion. The building has been preserved in the same state as immediately after the bombing, and now serves as the reminder of nuclear devastation and as a symbol of hope for world peace and elimination of all nuclear weapons. Fuente: wiki

El “Genbaku dome” fue el edificio más cercano al punto en el que explotó la bomba atómica de Hiroshima. Albergaba la cámara de comercio de la ciudad y su cúpula de bronce se fundió al instante con el calor de la bomba.

Los japoneses decidieron mantenerlo tal y como quedó como recuerdo de lo que ocurrió y el deseo de que no vuelva a pasar jamás.

The noise on this seismogram from the Snow King Mountain seismic station in Wyoming, USA represents shock waves from a magnitude 3.6 earthquake that hit in the Gros Ventre Mountains of northwestern Wyoming. According to the United States Geological Survey, the quake occurred at 3:43 AM, local time, on 24 February 2021, but this seismogram's signal starts before that. The epicenter was about 30 kilometers east-northeast of the town of Jackson (a.k.a. Jackson Hole), Wyoming. The hypocenter was about 7 kilometers deep.

This earthquake occurred only 7 miles east-southeast of the famous Gros Ventre Landslide. In June 1925, a large rockslide occurred in the Gros Ventre River Valley, triggered by an earthquake that followed weeks of rain. Several cubic miles of debris blocked the river. A five mile long, ~200 feet deep lake formed behind the landslide dam. Two years later, the dam was breached by erosion and a considerable flood swept downstream - this destroyed the town of Kelly, resulting in six deaths. The Gros Ventre Landslide scar is still visible today.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000dkmw/exec...

and

en.wikipedia.org/wiki/Gros_Ventre_landslide

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This is a seismogram for the Little Thumb Creek seismic station in Yellowstone, Wyoming. The prominent noise in the 09:30 line near the bottom of the graph (click on the image once or twice to zoom in) was caused by shock waves from a magnitude 7.4 earthquake that hit Oaxaca State in southern Mexico at 10:29 AM, local time, on 23 June 2020. Shock waves arrived at the seismic station at 9:35 AM, Yellowstone time, ~6 minutes after the quake hit.

The Mexican earthquake occurred along a subduction zone - such settings experience the most powerful tectonic quakes on Earth. In the far-eastern Pacific Ocean, the Cocos Plate, composed entirely of oceanic lithosphere, subducts beneath the North American Plate. The subduction zone's surface expression is a deep seafloor trough called the Middle America Trench.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000ah9t/exec...

and

en.wikipedia.org/wiki/2020_Oaxaca_earthquake

and

en.wikipedia.org/wiki/Cocos_Plate

and

en.wikipedia.org/wiki/Middle_America_Trench

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

The Atomic Bomb Dome serves as a memorial to the people who died in the atomic bombing of Hiroshima, Japan, in 1945. The building was the only structure left standing near the bomb’s hypocenter. Photo by Barbara Dunlap-Berg, UMNS

My mother and I visit Hiroshima, Japan, March 19, 2016.

Hiroshima Prefecture is located in the southwestern part of the Japanese islands. It is rich in the natural beauty of the Inland Sea and the Chugoku Mountains, with mountains, sea, rivers, valleys, plains, basins that characterize Japan's landscape.

Hiroshima Castle (広島城, Hiroshimajō), also called the Carp Castle, is a good example of a castle built on a plain in the center of a city as opposed to hilltop and mountaintop castles. Its main keep is five stories tall, and its grounds are surrounded by a moat. Also within the castle's precincts are a shrine, some ruins and a few reconstructed buildings of the Ninomaru (second circle of defense).

Hiroshima developed as a castle town, whereby the castle was both the physical and economical center of the city. Built in 1589 by the powerful feudal lord Mori Terumoto, Hiroshima Castle was an important seat of power in Western Japan. While it was spared the demolishment that many other castles met during the Meiji Restoration, like the rest of the city, Hiroshima Castle was destroyed by the atomic bomb in 1945.

The A-Bomb Dome is a symbol of peace which most people have at least seen at one time in a picture. The building, which was designed by a Czech architect in 1915, had been used as the Hiroshima Prefectural Industrial Promotion Hall. Hiroshima citizens back then loved so much European modern-style buildings of the time. In 1912, the National Confectionery Exposition was held in this place. From that exposition, Baumkuchen, which represented German cake, was manufactured and sold in Japan for the first time. Since the Hiroshima Prefectural Industrial Promotion Hall was located only around 160 meters from the hypocenter, the building was blown up, and all those inside the building died. However, the building was not destroyed completely because the blast of the atomic bomb, which was vaporized in the air, prevented it from totally collapsing. It was designated a UNESCO World Heritage Site in 1996 and has been representing people's prayers for a lasting peace.

Photo by John L. Carkeet IV, LimpingFog Productions

MR. KITA (Isao Kita): Well, at that time, I happened to be receiving the transmission over the wireless. I was in the receiving room and I was facing northward. I noticed the flashing light. It was not really a big flash. But still it drew my attention. In a few seconds, the heat wave arrived. After I noticed the flash, white clouds spread over the blue sky. It was amazing. It was as if blue morning-glories had suddenly bloomed up in the sky. It was funny, I thought. Then came the heat wave. It was very very hot. Even though there was a window glass in front of me, I felt really hot. It was as if I was looking directly into a kitchen oven. I couldn't bear the heat for a long time. Then I heard the cracking sound. I don't know what made that sound, but probably it came from the air which suddenly expanded in the room. By that time, I realized that the bomb had been dropped. As I had been instructed, I pushed aside the chair and lay with my face on the floor. Also as I had been instructed during the frequent emergency exercises, I covered my eyes and ears with hands like this. And I started to count. You may feel that I was rather heartless just to start counting. But for us, who observed the weather, it is a duty to record the process of time, of various phenomena. So I started counting with the light flash. When I counted to 5 seconds, I heard the groaning sound. At the same time, the window glass was blown off and the building shook from the bomb blast. So the blast reached that place about 5 seconds after the explosion. We later measured the distance between the hypocenter and our place. And with these two figures, we calculated that the speed of the blast was about 700 meters per second. The speed of sound is about 330 meters per second, which means that the speed of the blast was about twice as fast as the speed of sound. It didn't move as fast as the speed of light but it moved quite rapidly. There is a path which leads by here over there. And on that day, a large number of injured persons walked this way along the path toward the Omi Hospital. They were bleeding all over and some of them had no clothes. Many of them were carrying people on their shoulders. Looking at the injured, I realized how seriously the town had been damaged. The fire was its peak at around that time. It thundered 10 times between 10 and 11 o'clock. The sound of thunder itself was not so great but still I could see the lightning over the fire. When I looked down on the town from the top of that hill, I could see that the city was completely lost. The city turned into a yellow sand. It turned yellow, the color of the yellow desert.

INTERVIEWER: Was this before the fire broke out?

MR. KITA: Yes. The town looked yellowish. The smoke was so thick that it covered the entire town. After about 5 minutes, fire broke out here and there. The fire gradually grew bigger and there were smoke everywhere and so we could no longer see towards the town. The cloud of the smoke was very tall, but it didn't come in this direction at all. The cloud moved in that direction from the ocean towards Hiroshima Station. It moved towards the north.The smoke from the fire, it was like a screen dividing the city into two parts. The sun was shining brightly just like it was a middle of the summer over here on this side. And behind the cloud on the other side, it was completely dark. The contrast was very much. So about 60 or 70 % of the sky was covered by the cloud and the other 30 % was completely clear. It was a bright clear blue sky. The condition had remained like this for some time. From Koi, looking towards Hiroshima Station, you could see the black rain falling. But from here, I couldn't judge how much rain was falling. But based on the information I heard later, it seems that the rain fell quite heavy over a period of several hours. It was a black and sticky rain. It stuck everything. When it fell on trees and leaves, it stayed and turned everything black. When it fell on people's clothing, the clothing turned black. It also stuck on people's hands and feet. And it couldn't be washed off. I couldn't be washed off. I couldn't see what was taking place inside the burning area. But I was able to see the extent of the area which was on fire. Based on the information which came later, it seems that the center of the town suffered the worst damage. The atomic bomb does not discriminate. Of course, those who were fighting may have to suffer. But the atomic bomb kills everyone from little babies to old people. And it's not an easy death. It's a very cruel and very painful way to die. I think that this cannot be allowed to happen again anywhere in the world. I don't say this just because I'm a Japanese atomic bomb survivor. I feel that people all over the world must speak out.

[Childs voice:]

Look, Mummy. There's an airplane up in the sky.

Goodbye.

This is a seismogram from the Narrogin seismic station in Australia. The noise is from a magnitude 4.7 earthquake in the southern part of Western Australia. The quake hit at 1:12 PM, local time, on 5 January 2023.

--------------------------------

Info. at:

earthquake.usgs.gov/earthquakes/eventpage/us7000j285/exec...

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

広島大本営跡 被爆樹木 クロガネモチ A-Bombed tree Kurogane holly

flic.kr/p/eywnpg flic.kr/p/eyzyrU flic.kr/p/eywtKp

広島市中区基町 広島城址公園

Hiroshima castle ruins park, Moto-machi, Naka-ku, Hiroshima

Roughly 900 meters from the hypocenter

The garden area in front of the remains of the Imperial Military Headquarters. The building was completely destroyed by the atomic bomb. But Kurogane holly endured in the garden.

photozou.jp/photo/show/2140645/178858774

photozou.jp/photo/show/2140645/178858794

photozou.jp/photo/show/2140645/178858808

史跡 広島城 広島城址公園 広島市中区基町

二の丸表御門 www.panoramio.com/photo/91215463

Hiroshima castle second bailey (ninomaru) main gate flic.kr/p/eyyyaS

被爆樹木 ユーカリ A-Bombed tree Eucalyptus flic.kr/p/eyyNub

被爆樹木 マルバヤナギ A-Bombed tree Japanese pussy willow flic.kr/p/eyvMz2

本丸跡 石垣 central bailey honmaru, stone walls flic.kr/p/eyz1QS

中国軍管区司令部 地下通信室跡

Underground communication room of Chugoku Regional Military Headquarters

Remains of Chugoku Military District Headquarters

広島大本営跡 被爆樹木 クロガネモチ A-Bombed tree Kurogane holly

flic.kr/p/eywnpg flic.kr/p/eyzyrU flic.kr/p/eywtKp

広島大本営跡 ruins of Imperial Headquarters in Hiroshima www.panoramio.com/photo/91153347 flic.kr/p/eyvYF6

広島城 Hiroshima Castle www.panoramio.com/photo/87561876 www.panoramio.com/photo/87561876 flic.kr/p/ez16gp

広島護国神社 Hiroshima Gokoku Shrine www.panoramio.com/photo/91105666 flic.kr/p/eyuTqp

神馬 sacred horse www.panoramio.com/photo/91105689 flic.kr/p/eyuTtM

These are seismograms for the Maple Creek and Parker Peak seismic stations in Yellowstone, Wyoming. The prominent noise on the 04:00 lines (click on the image once or twice to zoom in) was caused by shock waves from a magnitude 6.0 earthquake. It occurred in the eastern Fiji Islands in the South Pacific Ocean at 10:11 PM, local time, on 6 October 2020. Seismic waves reached the stations at 4:23 AM, Yellowstone time, ~12 minutes after the quake hit. The hypocenter was about 628 kilometers deep, a very considerable depth. This was a deep-focus, subduction zone earthquake. Subduction zones involve one tectonic plate composed of oceanic lithosphere diving beneath a plate of continental or oceanic lithosphere.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000c617/exec...

and

earthquake.usgs.gov/earthquakes/eventpage/us6000c617/regi... (scroll down to read info.)

and

en.wikipedia.org/wiki/Deep-focus_earthquake

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This is a seismogram from the Lhasa seismic station in Tibet. The noise on the 17:00 line was caused by shock waves from a magnitude 5.5 earthquake that hit the Tibetan Plateau in western China. The quake occurred at 1:27 AM, local time, on 30 March 2021. The epicenter was about 517 kilometers northwest of the town of Nagqu, Tibet. The hypocenter was at about 8 kilometers depth.

Tibet is part of a tectonic collision zone that is centered in the Himalayan Mountains of northern India and Nepal. The subcontinent of India used to be a large island - it collided with Asia during the Tertiary, forming the Himalayas, the highest mountains on Earth. Significant uplift also occurred in adjacent Tibet

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000dxge/exec...

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

These are seismograms for the St. George's, Bermuda and Presa de Sabenta, Dominican Republic and Gun Hill, Barbados seismic stations. The noise on the 7:00 lines (click on the image once or twice to zoom in) was caused by shock waves from a magnitude 5.0 earthquake that hit offshore from the Virgin Islands in the western Atlantic Ocean. The quake occurred at 3:05 AM, local time, on 6 February 2021. The epicenter was about 65 kilometers northwest of Anegada Island. The hypocenter was about 78 kilometers deep.

The smaller signal at the very left end of the 7:00 lines is from a magnitude 4.4 foreshock event nine minutes earlier, at 2:56 AM. The small signal near the right end of the 12:00 lines is from an aftershock event. Foreshocks started occurring late on 5 February 2021. As of this writing, 22 earthquakes have occurred in the same area, most of which are aftershocks to the 5.0 main event.

This was a subduction zone earthquake. Subduction zones have a tectonic plate composed of oceanic lithosphere diving underneath a plate of continental or oceanic lithosphere. In this case, oceanic lithosphere of the North American Plate is subducting westward under the Caribbean Plate. Subduction zones have the most powerful tectonic quakes in the world. Quakes and volcanism are common geologic hazards in such settings. Here, the subduction zone itself is a deep seafloor trough called the Puerto Rico Trench.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/pr2021037002/ex...

and

earthquake.usgs.gov/earthquakes/eventpage/pr2021037002/re... [Scroll down for a tectonic summary of the Caribbean region.]

and

earthquake.usgs.gov/earthquakes/tectonic/images/caribbean...

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

P = P-waves (primary waves)

S = S-waves (secondary waves)

-------------------------------------------------

This is a seismogram from the M52A seismic station in Ohio, USA. The noise was caused by a magnitude 2.3 earthquake that hit Lake Erie, 2 to 3 kilometers west-northwest of (offshore from) the town of Timberlake, northeastern Ohio. The quake occurred at 3:53 AM, local time, on 27 January 2022. The hypocenter was about 2 kilometers deep.

The United States Geological Survey assigned a magnitude value of 2.1 to this quake, and a hypocenter depth of almost 7 kilometers. The Ohio Geological Survey reported the quake at magnitude 2.3 and a hypocenter depth of almost 2 kilometers.

Ohio earthquakes are rare and usually small in magnitude. Two areas in Ohio have more frequent quakes than elsewhere: 1) western Ohio and 2) northeastern Ohio.

--------------------------------

From Dart & Hansen (2008) - Earthquakes in Ohio and vicinity, 1776-2007. United States Geological Survey Open-File Report 2008-1221:

The Northeast Ohio seismic zone has had moderately frequent earthquakes at least since the first one was reported in 1836. The largest earthquake in this zone (magnitude 5.0) occurred in 1986. This event produced Modified Mercalli intensities of VI in the epicentral region. A damaging earthquake (magnitude 5.2) occurred in 1998 near Pymatuning in northwestern Pennsylvania, just east of the Ohio border. An earthquake in the Ashtabula, Ohio area (magnitude 4.3) in 2001 caused minor damage. Historically, this zone has recorded only a few earthquakes per decade, but felt earthquakes have been reported more frequently in recent decades. This is probably a result of increased population, greater public awareness, improved communications, and perhaps episodic seismicity.

--------------------------------

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us7000gfj0/exec...

and

ohiohistorycentral.org/w/Earthquakes

and

c2.staticflickr.com/4/3768/32761626386_11098c17da_o.gif

and

www.flickr.com/photos/jsjgeology/51317417047

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

So these three students came running up to my group (3 of us) in the middle of Peace Park in Nagasaki. The survey on their clipboards read "Foreigner opinion of Obama nuclear arms policy" and the first thing through my head was "ok, well, awkward, but didn't these three just hit the jackpot! THE three Americans to come through the park on a sleepy Saturday afternoon" They were most happy to pose for a picture after we completed the surveys

This is a seismogram for the Norris Junction seismic station in Yellowstone, Wyoming. The prominent noise about one-third up from the bottom of the graph (click on the image once or twice to zoom in) was caused by shock waves from a magnitude 6.5 earthquake that hit western Nevada at 4:03 AM, local time, on 15 May 2020. The shock waves first arrived at the seismic station at about 5:05 AM, Yellowstone time, which is ~2 minutes after the quake hit. The United States Geological Survey reports that the earthquake's hypocenter was at 2.8 kilometers depth, which is shallow. The epicenter is at 38° 09' 32" North latitude, 117° 52' 30" West longitude. This is at an alluvial fan on the western flanks of the Monte Cristo Range in Esmeralda County, Nevada. Mountain ranges in Nevada are "horsts" - crustal blocks that have moved upward by normal faulting. Adjacent valleys are "grabens" - crustal blocks that have moved downward. Each mountain range and valley in Nevada is bordered by a major normal fault. Nevada is at the heart of a large region of crustal extension called the Basin and Range Physiographic Province. Crustal stretching here has occurred throughout the Cenozoic Era.

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This is a seismogram from the Kilima Mbogo seismic station in Kenya. The prominent red noise on the 05:30 line (click on the image once or twice to zoom in) represents shock waves from a magnitude 4.7 earthquake that hit southwestern Tanzania in eastern Africa. The quake occurred at 8:49 AM, local time, on 15 October 2021. The epicenter was about 10.5 kilometers south-southeast of the town of Kaoze, Tanzania.

This earthquake occurred in the Rukwa Trough, a branch of the East African Rift Valley. Eastern Africa is being ripped apart by the Afar Hotspot. Two rift branches radiating from the hotspot are so deep that they've been flooded by the oceans - the Red Sea and the Gulf of Aden. The East African Rift Valley is a third rift branch - it extends ~southward into Africa. In places, the rift valley is deep enough to host lakes. In the far future, it will also be flooded by seawater. Earthquakes occur throughout the rift system. Active and potentially active volcanoes are also present.

The magnitude 4.7 Tanzania quake took place at the southern margin of the Rukwa Trough, south of Lake Rukwa. It appears to have occurred from a jolt of movement along the Ufipa Fault, a major normal fault that separates the Rukwa Trough from the Ufipa Plateau.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000fute/exec...

and

en.wikipedia.org/wiki/East_African_Rift

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This is a seismogram from the Kabul seismic station in Afghanistan. The noise is from a magnitude 6.8 earthquake that hit the Pamir Mountains of eastern Tajikistan, central Asia. The quake occurred at 5:37 AM, local time, on 23 February 2023. The hypocenter was about 20 kilometers deep.

The Pamir Mountains are part of a widespread orogenic zone formed by tectonic collision. The Indian Subcontinent, which is part of the Indian-Australian Plate, collided with Asia during the Tertiary and produced the Himalayas, the highest mountains in the world. The collision event resulted in extensive mountain building in areas distal and peripheral to the Himalayas, including the Pamir Mountains, where this quake occurred. In this case, shaking resulted from normal faulting, rather than reverse or thrust faulting.

--------------------------------

Info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000jqxc/exec...

and

en.wikipedia.org/wiki/Pamir_Mountains

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This seismogram is from the Fort St. James seismic station in western Canada. The noise on the right is from a magnitude 5.0 earthquake that hit Alberta, Canada at 8:59 AM, local time, on 16 March 2023. The epicenter was about 47 kilometers east-southeast of the town of Peace River, Canada. Shaking resulted from reverse faulting along a northwest-southeast striking fault zone. The noise on the left is a magnitude 4.8 foreshock that occurred 12 to 13 minutes earlier.

--------------------------------

Info. at:

earthquake.usgs.gov/earthquakes/eventpage/us7000jkfd/exec...

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This is a seismogram from the Kilima Mbogo seismic station in Kenya. The red noise on the 01:30 line was caused by a magnitude 6.2 earthquake that hit the island of Sumatra in Indonesia. The quake occurred at 9:39 AM, local time, on 25 February 2022. The epicenter was at the town of Salibawan in the Barisan Mountains. The hypocenter was between 10 and 15 kilometers deep. Shaking resulted from strike-slip motion along a northwest-southeast or a northeast-southwest trending fault zone. The zig-zag pattern on the 02:00 line represents Rayleigh waves.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000gzyg/exec...

and

en.wikipedia.org/wiki/Barisan_Mountains

and

en.wikipedia.org/wiki/Sunda_Plate

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

広島大本営跡 被爆樹木 クロガネモチ A-Bombed tree Kurogane holly

flic.kr/p/eywnpg flic.kr/p/eyzyrU flic.kr/p/eywtKp

広島市中区基町 広島城址公園

Hiroshima castle ruins park, Moto-machi, Naka-ku, Hiroshima

Roughly 900 meters from the hypocenter

The garden area in front of the remains of the Imperial Military Headquarters. The building was completely destroyed by the atomic bomb. But Kurogane holly endured in the garden.

photozou.jp/photo/show/2140645/178858774

photozou.jp/photo/show/2140645/178858794

photozou.jp/photo/show/2140645/178858808

史跡 広島城 広島城址公園 広島市中区基町

二の丸表御門 www.panoramio.com/photo/91215463

Hiroshima castle second bailey (ninomaru) main gate flic.kr/p/eyyyaS

被爆樹木 ユーカリ A-Bombed tree Eucalyptus flic.kr/p/eyyNub

被爆樹木 マルバヤナギ A-Bombed tree Japanese pussy willow flic.kr/p/eyvMz2

本丸跡 石垣 central bailey honmaru, stone walls flic.kr/p/eyz1QS

中国軍管区司令部 地下通信室跡

Underground communication room of Chugoku Regional Military Headquarters

Remains of Chugoku Military District Headquarters

広島大本営跡 被爆樹木 クロガネモチ A-Bombed tree Kurogane holly

flic.kr/p/eywnpg flic.kr/p/eyzyrU flic.kr/p/eywtKp

広島大本営跡 ruins of Imperial Headquarters in Hiroshima www.panoramio.com/photo/91153347 flic.kr/p/eyvYF6

広島城 Hiroshima Castle www.panoramio.com/photo/87561876 www.panoramio.com/photo/87561876 flic.kr/p/ez16gp

広島護国神社 Hiroshima Gokoku Shrine www.panoramio.com/photo/91105666 flic.kr/p/eyuTqp

神馬 sacred horse www.panoramio.com/photo/91105689 flic.kr/p/eyuTtM

This is a seismogram from the Otavalo seismic station in Ecuador. The prominent noise was caused by shock waves from a magnitude 6.1 earthquake that hit offshore from the southern coastline of Panama, in the far-eastern Pacific Ocean. The quake occurred at 2:56 PM, local time, on 17 July 2021. The epicenter was about 103 kilometers west-southwest of Jicarita Island. The hypocenter was at about 9 kilometers depth.

The quake was due to right-lateral slip along a north-south striking, subvertically-oriented transform fault in the Panama Transform Fault system (often mis-referred to as the Panama Fracture Zone). The Panama Transform Fault is the eastern boundary of the Cocos Plate and the western boundary of the Coiba Microplate. Transform faults occur where two tectonic plates slide past each other - the most famous example is California's San Andreas Fault.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us7000emzy/exec...

and

en.wikipedia.org/wiki/Panama_Fracture_Zone

and

en.wikipedia.org/wiki/Coiba_Plate

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

We want you

and the people everywhere

to know what happened

that day

before the eyes of this child.

(Nagasaki, about 0.7 miles from the hypocenter, August 10 1945 - Photo: Yosuke Yamahata)

This seismogram is from the Hachijo Island seismic station in the Izu Islands, south of Japan. The noise is from a magnitude 6.3 offshore earthquake that hit south of Japan at 1:49 PM, local time, on 16 January 2023. The epicenter was about 353 kilometers ~northwest of Chichi Island in the Ogasawara Islands, south of Japan. The hypocenter was between 400 and 410 kilometers deep - a considerable depth. Quakes deeper than 300 kilometers are called "deep-focus earthquakes". The earthquake resulted from normal faulting west of the Izu-Bonin Trench, a deep seafloor trough formed by the Pacific Plate subducting westward beneath the Philippines Plate.

--------------------------------

Info. at:

earthquake.usgs.gov/earthquakes/eventpage/us7000ipkm/exec...

and

en.wikipedia.org/wiki/Izu–Ogasawara_Trench

and

en.wikipedia.org/wiki/Deep-focus_earthquake

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This seismogram is from the Yuzhno Sakhalinsk seismic station on Sakhalin Island, Russia. The prominent noise on the 4:00 line is from a magnitude 5.7 offshore earthquake that hit Alaska's far-western Aleutian Islands. The quake occurred at 2:57 PM, local time, on 29 December 2021. The epicenter was about 250 kilometers northwest of Attu Island. The hypocenter was shallow - between 3 and 4 kilometers deep. Movement was right-lateral slip along a WNW-ESE striking, subvertical fault zone. The noise on the 9:00 line is a magnitude 5.0 aftershock in the same area.

The Aleutian Islands are an extensive volcanic arc formed along a subduction zone, where one tectonic plate dives beneath another. In this case, oceanic lithosphere of the Pacific Plate is subducting below the North American Plate. Earthquakes and volcanism are common along such plate boundaries. The surface expression of the subduction zone itself is a deep seafloor trough called the Aleutian Trench. In the eastern Aleutians, subduction is nearly perpendicular to the volcanic arc. In the western Aleutians, where this earthquake occurred, subduction is at a very low angle to the trend of the arc - the Pacific and North American Plates are almost sliding past each other (close to transform movement).

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000gg09/exec...

and

earthquake.usgs.gov/earthquakes/eventpage/us6000gg2x/exec...

and

en.wikipedia.org/wiki/Aleutian_Trench

and

en.wikipedia.org/wiki/Aleutian_Arc

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This seismogram is from the Las Campanas Astronomical Observatory seismic station in Chile. The noise on the 6:00 line is from a magnitude 6.0 earthquake that hit northern Argentina at 3:12 AM, local time, on 22 February 2022. The epicenter was about 40 kilometers southwest of Pozuelo Lake. The hypocenter was between 240 and 245 kilometers deep.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us7000gmw3/exec...

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

Hiroshima, Japan

These are seismograms for the Maple Creek, Parker Peak, and Little Thumb Creek seismic stations in Yellowstone, Wyoming. The prominent noise on the 00:00 lines (click on the image once or twice to zoom in) was caused by shock waves from a magnitude 5.7 earthquake that hit offshore Oregon on the western coast of North America at 11:10 PM, local time, on 28 December 2020. Shock waves arrived at the seismic station at 12:13 AM on 29 December 2020, Yellowstone time, about 3 minutes after the quake hit.

This event occurred along the eastern segment of the Bianco Transform Fault (often mis-referred to as the Bianco Fracture Zone - fractures zones are extensions of transform faults away from mid-ocean ridges - "fracture zone" is not the term for a transform fault itself). The Bianco Transform Fault connects the Juan de Fuca Ridge and the Gorda Ridge, where new oceanic crust is forming. Transform faults are fractures along which two tectonic plates slide past each other, although movement is usually in the form of sudden jolts - earthquakes. The most famous transform fault in the world is California's San Andreas Fault. The Bianco Transform Fault is the boundary zone between the Pacific Plate and the Juan de Fuca Plate, both of which are composed of oceanic lithosphere.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000d3xn/exec...

and

en.wikipedia.org/wiki/Blanco_Fracture_Zone

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This seismogram is from the Mercer Wildlife Area seismic station in Mercer County, Ohio, USA. The noise was caused by a magnitude 2.4 earthquake that hit northeastern Darke County in western Ohio. The quake occurred at 7:39 PM, local time, on 1 January 2023. The epicenter was about 0.8 to 0.9 kilometers ~east of Frenchtown, Ohio & ~3.5 kilometers northwest of the town of Versailles, Ohio. The hypocenter was between 5 and 10 kilometers deep.

Ohio earthquakes are rare and usually small in magnitude. Two areas in Ohio have more frequent quakes than elsewhere: 1) western Ohio and 2) northeastern Ohio.

--------------------------------

Info. at:

earthquake.usgs.gov/earthquakes/eventpage/se60500248/exec...

and

ohiohistorycentral.org/w/Earthquakes

and

c2.staticflickr.com/4/3768/32761626386_11098c17da_o.gif

and

www.flickr.com/photos/jsjgeology/51317417047

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This is a seismogram from the Pulkovo seismic station in western Russia. The noise is from a magnitude 4.4 earthquake that hit the Kola Peninsula in far-northwestern Russia at 3:13 AM, local time, on 5 March 2022. The epicenter was at the Koashva mining operation just west of Lake Umbozero.

The Koashva Mine principally targets apatite (a calcium phosphate mineral) for its phosphorus content, which is an ingredient in agricultural fertilizer. Seismicity in the Kola Peninsula mining districts has been previously reported (e.g., Kozyrev et al., 2005).

--------------------------------

Reference cited:

Kozyrev et al. (2005) - Mining-induced earthquakes in the open pits of the Kola Peninsula. pp. 575-577 in: Controlling Seismic Risk. Sixth International Symposium on Rockburst and Seismicity in Mines Proceedings.

--------------------------------

Info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000h27r/exec...

and

www.mindat.org/loc-2672.html

and

papers.acg.uwa.edu.au/p/574_64_Kozyrev/

--------------------------------

An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

a 3d fully rotatable (H and V), from any point, view of 19000 odd quake hypocenters over 3 years, under the north island of nz. The low edge of the zone is aprox 270km below the surface. Some quakes occur at double that depth well down in the mantle. Lucky we only feel a few of the larger events, mainly from that 'shallow' level in the first 25km.

A home built software project.

This is a seismogram from the South Karori seismic station in New Zealand. The prominent noise was caused by shock waves from a magnitude 6.3 earthquake that hit in the Kermadec Islands area of the southwestern Pacific Ocean. The quake occurred at 2:52 PM, local time, on 31 August 2021. The epicenter was about 90 kilometers southeast of Raoul Island. The hypocenter was about 16 kilometers deep.

This was a subduction zone earthquake. Subduction zones involve one tectonic plate composed of oceanic lithosphere diving underneath another tectonic plate. In this case, the Pacific Plate is subducting ~westward beneath the Australian Plate. The surface expression of the subduction zone is a deep seafloor trough called the Kermadec Trench.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us7000f60j/exec...

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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This is a seismogram for the San Rafael Swell seismic station in Utah. The prominent noise on the 16:30 to 18:00 lines (click on the image once or twice to zoom in) was caused by body waves and surface waves from a magnitude 7.0 (revised from 6.9) subsea earthquake that hit next to the Wordie Seamount in the Bransfield Basin, offshore from the South Shetland Islands, near Antarctica. The epicenter is 33 to 34 kilometers ~south of Gibbs Island. The quake occurred at 7:36 PM, local time, on 23 January 2021. The hypocenter was between 9 and 10 kilometers deep.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us7000d2rx/exec...

and

en.wikipedia.org/wiki/Bransfield_Basin

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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This is a seismogram from the Honiara station in the Solomon Islands. The prominent noise represents shock waves from a magnitude 6.0 earthquake that occurred offshore from the Santa Cruz Islands (= north of Vanuatu & east of the Solomon Islands in the western Pacific Ocean). The quake hit at 11:04 PM, local time, on 25 November 2021. The epicenter was about 41 kilometers east of the island of Nendo. The hypocenter was about 40 kilometers deep.

This earthquake occurred near the North New Hebrides Trench area, which is a subduction zone. Subduction involves a tectonic plate composed of oceanic lithosphere diving beneath another tectonic plate. In this case, the Indian-Australian Plate is subducting ~northeastward beneath the New Hebrides Plate. This quake was actually the result of strike-slip movement along a nearly vertical fault that strikes north-northwest to south-southeast or east-northeast to west-southwest.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us7000fwzz/exec...

and

en.wikipedia.org/wiki/New_Hebrides_Plate

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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

WRAB = Warramunga seismic station at Tennant Creek, Australia

TLY = Talaya seismic station in Russia

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The prominent noise on the middle line of these two seismograms (click on the image once or twice to zoom in) was caused by shock waves from a magnitude 6.3 earthquake that occurred in the Bismarck Sea, offshore from the islands of New Guinea & New Britain in the western Pacific Ocean, at 3:45 PM, local time, on 7 February 2021. The epicenter was about 150 kilometers southwest of Manus Island. The hypocenter was about 14 kilometers deep.

The earthquake occurred along the Bismarck Sea Seismic Lineation, which marks the boundary between two microplates, the North Bismarck Plate and the South Bismarck Plate.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000dfad/exec...

and

earthquake.usgs.gov/earthquakes/eventpage/us6000dfad/regi... [Scroll down for a tectonic summary of the region.]

and

earthquake.usgs.gov/earthquakes/tectonic/images/newguinea...

and

en.wikipedia.org/wiki/North_Bismarck_Plate

and

en.wikipedia.org/wiki/South_Bismarck_Plate

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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This is a seismogram from the Ny-Alesund seismic station in Spitzbergen (Svalbard). The noise on the 4:00 line was caused by shock waves from a magnitude 5.5 offshore earthquake that hit in the Fram Strait (= northern Greenland Sea), between Spitzbergen and Greenland. The quake occurred at 4:05 AM, local time, on 23 July 2021. The epicenter was about 304 kilometers northwest of the town of Longyearbyen. Another earthquake of similar magnitude occurred in the area four months earlier, on 23 March 2021 (see: www.flickr.com/photos/jsjgeology/51066977673 ).

The earthquake occurred near the southeastern end of the Spitzbergen Transform Fault (frequently mis-referred to as the Spitzbergen Fracture Zone), which offsets spreading centers between the Knipovich Ridge (to the south) and the Gakkel Ridge (to the north). Mid-ocean ridges are seafloor mountain ranges formed by tectonic divergence - two plates separate from each other and new basaltic oceanic crust forms. In map view, mid-ocean ridges have a zig-zag pattern, because the ridges are offset by numerous short to long transform faults. The Spitzbergen Transform Fault is about 150 kilometers long.

The noise at the bottom of the chart is from a magnitude 6.7 subduction zone earthquake in the Philippines. Both quakes on the seismogram occurred during a Moon-Earth-Sun alignment.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000ey6s/exec...

and

en.wikipedia.org/wiki/Fram_Strait

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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

These maps (provided by the United States Geological Survey) show an earthquake swarm in northern Yellowstone Lake, Wyoming, USA in late March 2023. Magnitudes ranged from +3.7 to -0.1. The upper map has 88 earthquakes that occurred on 29 March 2023. The lower map has 107 earthquakes that occurred from 29 March to 1 April 2023.

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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.

This is a seismogram from the Tsumeb seismic station in Namibia. The noise on the 1:00 line represents shock waves from a magnitude 5.4 earthquake that hit northwestern Namibia in southwestern Africa. The quake occurred at 3:41 AM, local time, on 4 April 2021. The epicenter was 29 to 30 kilometers southwest of the town of Kamanjab, Namibia.

This earthquake was not located along or near a modern plate boundary. Namibia is part of Africa's stable craton, but intraplate earthquakes do take place in many parts of the world. The quake occurred in the Kamanjab Inlier, a large region of exposed, Precambrian-aged basement rocks. This is east of the Etendeka Traps (Etendeka Plateau Basalts), a Cretaceous-aged flood basalt deposit formed as South America rifted away from Africa during the breakup of the Pangaea supercontinent.

See info. at:

earthquake.usgs.gov/earthquakes/eventpage/us6000dyuk/exec...

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An earthquake is a natural shaking or vibrating of the Earth caused by sudden fault movement and a rapid release of energy. Earthquake activity is called "seismicity". The study of earthquakes is called "seismology". The actual underground location of an earthquake is the hypocenter, or focus. The site at the Earth's surface, directly above the hypocenter, is the epicenter. Minor earthquakes may occur before a major event - such small quakes are called foreshocks. Minor to major quakes after a major event are aftershocks.

Most earthquakes occur at or near tectonic plate boundaries, such as subduction zones, mid-ocean ridges, collision zones, and transform plate boundaries. They also occur at hotspots - large subsurface mantle plumes (Examples: Hawaii, Yellowstone, Iceland, Afar).

Earthquakes generate four types of shock waves: P-waves, S-waves, Love waves, and Rayleigh waves. P-waves and S-waves are body waves - they travel through solid rocks. Love waves and Rayleigh waves travel only at the surface - they are surface waves. P-waves are push-pull waves that travel quickly and cause little damage. S-waves are up-and-down waves (like flicking a rope) that travel slowly and cause significant damage. Love waves are side-to-side surface waves, like a slithering snake. Rayleigh waves are rotational surface waves, somewhat like ripples from tossing a pebble into a pond.

Earthquakes are associated with many specific hazards, such as ground shaking, ground rupturing, subsidence (sinking), uplift (rising), tsunamis, landslides, fires, and liquefaction.

Some famous major earthquakes in history include: Shensi, China in 1556; Lisbon, Portugal in 1755; New Madrid, Missouri in 1811-1812; San Francisco, California in 1906; Anchorage, Alaska in 1964; and Loma Prieta, California in 1989.