Central Indian Ridge magnitude 6.7 earthquake (6:05 PM, 12 May 2021) : 無料・フリー素材/写真
Central Indian Ridge magnitude 6.7 earthquake (6:05 PM, 12 May 2021) / 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 | This is a seismogram from the Tsumeb seismic station in Namibia. The prominent noise was caused by shock waves from a magnitude 6.7 offshore earthquake that hit below the seafloor in the Indian Ocean. The quake occurred at 6:05 PM, local time, on 12 May 2021. Various earthquake reporting agencies have assigned magnitude values ranging from 6.0 to 6.7. The epicenter was ~1780 kilometers east of the coast of Madagascar and ~410 kilometers northeast of Rodrigues Island. The hypocenter was over 20 kilometers deep.The quake occurred along the Marie Celeste Transform Fault (also known as the Mary Celeste Transform Fault; frequently mis-referred to as the Marie Celeste or Mary Celeste Fracture Zone), an approximately 270 kilometers-long transform fault that offsets spreading centers of the Central Indian Ridge. Mid-ocean ridges are seafloor mountain ranges developed where tectonic plates separate (= tectonic divergence) and new basaltic oceanic crust forms. Fault movement that caused this earthquake was left-lateral slip along a subvertically-oriented transform fault.See info. at:earthquake.usgs.gov/earthquakes/eventpage/us7000e2ec/exec...anden.wikipedia.org/wiki/Central_Indian_Ridge--------------------------------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 | 2021-05-13 13:26:22 |
| 撮影者 | James St. John |
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