Offshore Vancouver Island, Canada magnitude 6.2 earthquake (9:30 PM, 3 July 2019) : 無料・フリー素材/写真
Offshore Vancouver Island, Canada magnitude 6.2 earthquake (9:30 PM, 3 July 2019) / 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 the seismogram for the Little Thumb Creek seismic station in Yellowstone, Wyoming. The station is north-northwest of the West Thumb Geyser Basin. The prominent noise in the lower part of the graph was caused by shock waves from a magnitude 6.2 earthquake that hit offshore from Vancouver Island, Canada at 9:30 PM local time (= 10:30 PM Yellowstone time) on 3 July 2019. The shock waves first arrived at the seismic station at 10:34 PM, Yellowstone time, four minutes after the quake hit. The earthquake's locality is a subduction zone - one tectonic plate, composed of heavy oceanic lithosphere, is diving below another plate composed of lightweight continental lithosphere. In this case, the northernmost Juan de Fuca plate is diving (eastward & downward) below the North American Plate. The epicenter is at 51° 13' 19" North latitude, 130° 30' 54" West longitude, just beyond Queen Charlotte Sound, between Vancouver Island and the Queen Charlotte Islands, off Canada's southwestern coast.--------------------------------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 | 2019-07-04 05:28:04 |
| 撮影者 | James St. John |
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