New Hebrides Trench magnitude 7.7 earthquake (12:19 AM, 11 February 2021) 4 : 無料・フリー素材/写真
New Hebrides Trench magnitude 7.7 earthquake (12:19 AM, 11 February 2021) 4 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | The noise on this seismogram from the Shade River State Forest seismic station in Meigs County, southeastern Ohio, USA represents shock waves from a powerful magnitude 7.7 earthquake that occurred in the New Hebrides Trench in the southwestern Pacific Ocean. Nearby major islands and archipelagos include New Caledonia, the Loyalty Islands, Vanuatu, and Fiji. The main shock hit at 12:19 AM, local time, on 11 February 2021. The epicenter was about 112 kilometers south-southwest of Hunter Island and 379 kilometers south-southeast of Anatom Island. The hypocenter was between 25 and 26 kilometers deep. Many strong aftershocks in the 5s and 6s occurred afterward.Signal noise on the diagram that precedes the 7.7 quake is from one or more strong earthquakes that occurred in the previous hour: 6.0 and 6.1 foreshock events in the New Hebrides Trench and a 6.2 quake in Indonesia.This was a global event - significant noise was recorded at every functioning seismic station I've looked at.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 beneath the Pacific Plate.See info. at:earthquake.usgs.gov/earthquakes/eventpage/us6000dg77/exec... [Scroll down to read event-specific and general tectonic summaries.] --------------------------------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. |
| 撮影日 | 2021-02-10 13:47:34 |
| 撮影者 | James St. John |
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