Sea of Marmara magnitude 6.2 earthquake (12:49 PM, 23 April 2025) + aftershocks 1 : 無料・フリー素材/写真
Sea of Marmara magnitude 6.2 earthquake (12:49 PM, 23 April 2025) + aftershocks 1 / 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 seismogram, from the Gratini seismic station in northeastern Greece, shows an earthquake sequence on 23 April 2025 in the Sea of Marmara in Turkey. The main shock at left was a magnitude 6.2 offshore earthquake at 12:49 PM, local time. Significant aftershocks in the following three hours were events in the 4s and 5s. The main shock resulted from right-lateral slip along an ~east-west striking transform fault called the North Anatolian Fault, which is below a negative flower structure in the Sea of Marmara area (see Aksu et al., 2000). Flower structures are large-scale, upward-branching fault zones. Positive flower structures have topographic highs above them. Negative flower structures form surface basins.The North Anatolian Transform Fault is the plate boundary between the Aegean-Anatolian Plate (= most of Turkey, and parts of Greece and the Mediterranean Sea) and the Eurasian Plate.--------------------------------Reference cited:Aksu et al. (2000) - Anatomy of the North Anatolian Fault Zone in the Marmara Sea, western Turkey: extensional basins above a continental transform. GSA Today 10(6): 3-7.--------------------------------Info. at:earthquake.usgs.gov/earthquakes/eventpage/us7000pufs/exec...anden.wikipedia.org/wiki/North_Anatolian_Fault--------------------------------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 | 2025-04-23 13:58:21 |
| 撮影者 | James St. John |
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