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A seismogram recorded in Massachusetts, United States. The magnitude 9.1 (M w) undersea megathrust earthquake occurred on 11 March 2011 at 14:46 JST (05:46 UTC) in the north-western Pacific Ocean at a relatively shallow depth of 32 km (20 mi), [9] [56] with its epicenter approximately 72 km (45 mi) east of the Oshika Peninsula of Tōhoku, Japan, lasting approximately six minutes.
The basis for defining this tectonic boundary is the occurrence of large magnitude 7 or greater earthquakes along a linear zone from offshore Niigata Prefecture to off the west coast of Hokkaido. [7] Following the 1983 Nihonkai-Chubu earthquake , the idea of a young plate boundary was proposed, but its mechanism is unknown—it has been ...
This is a considerably simpler and thinner plate-boundary fault than has been observed at other locations, [16] such as the Nankai Trough. The actual slip surface for the 2011 earthquake may not have been recovered, but it is assumed that the structures and physical properties of the core are representative of the entire fault zone.
A series of M7 earthquakes occurred at the Fukushima-oki region in 1938, registering five in total. The magnitudes were 7.4, 7.7, 7.8, 7.7 and 7.1. [5] During December 1994, transient crustal movements were recorded by a Global Positioning System (GPS) network after an inter-plate earthquake arose within the Japan Trench.
The boundary between Okhotsk microplate and Pacific plate is a subduction zone, where the Pacific plate subducts beneath the Okhotsk Plate. Many strong megathrust earthquakes occurred here, some of them among the largest on world record, including the Kamchatka earthquakes of 1737 (estimated M9.0~9.3) and 1952 (M9.0).
Earthquakes occur where the Pacific plate meets the plate beneath northern Honshu in a subduction zone. [15] The Pacific plate, which moves at a rate of 8 to 9 cm (3.1 to 3.5 in) per year, dips under Honshu's underlying plate releasing large amounts of energy.
Convergent boundaries are areas where plates move toward each other and collide. These are also known as compressional or destructive boundaries. Obduction zones occurs when the continental plate is pushed under the oceanic plate, but this is unusual as the relative densities of the tectonic plates favours subduction of the oceanic plate. This ...
In Japan, the Shindo scale is commonly used to measure earthquakes by seismic intensity instead of magnitude. This is similar to the Modified Mercalli intensity scale used in the United States or the Liedu scale used in China, meaning that the scale measures the intensity of an earthquake at a given location instead of measuring the energy an earthquake releases at its epicenter (its magnitude ...