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Focal Mechanisms Statistics in Spatiotemporal Vicinity of the 2011 Tohoku Catastrophic Earthquakeстатья
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 20 мая 2020 г.
- Авторы: Lukk A.A., Leonova V.G.
- Журнал: Izvestiya. Physics of the Solid Earth
- Том: 56
- Номер: 2
- Год издания: 2020
- Издательство: Pleiades Publishing, Inc.
- Местоположение издательства: New York, USA
- Первая страница: 169
- Последняя страница: 188
- Оригинальные версии: Статистика фокальных механизмов в пространственно-временной окрестности катастрофического землетрясения 2011 года в Тохоку (Япония
- DOI: 10.1134/S1069351320020056
- Аннотация: Abstract—Statistical analysis of the focal mechanisms of the earthquakes based on the ISC standard catalogfor 2001 to 2017 is carried out in the spatiotemporal vicinity of epicentral zone of the catastrophic seismicevent of 2011 with Mw = 9.0 in Tohoku, Japan. It is established that during the 10-year period preceding thisearthquake, more than 80% of the intermediate (B) axes of the focal mechanisms of the earthquakes in thedepth interval from 0 to 65 km have a dip angle of at most 20° and are mainly oriented within the azimuthalsector from 190° to 210° enclosing the strike of the Japan Oceanic Trench. More than 75% of the pressureaxes (P) are inclined to the horizon at 5°–35°, and more than 75° of the axes of tension (T) have a dip anglefrom 50° to 80°. This orientation of the principal axes of focal mechanisms unambiguously suggests the predominanceof thrusting or underthrusting regime at these depths. This corresponds to the well-known tectonichypothesis that the Pacific Ocean lithospheric plate subducts beneath the continental Okhotsk plate inthe region of the Islands of Japan in the approximately sublatitudinal direction. The mega-thrust slip in thesource of the catastrophic Tohoku earthquake also corresponds to this type of the focal mechanism. A similartype of the focal mechanism was also observed in the aftershock sequence of the earthquakes located in thevicinity of the surface separating the hanging and subducting edges of the lithospheric plates colliding here,exactly at the location of the catastrophic earthquake. The predominant depth range of these earthquakes is30 to 55 km. At the same time, it is established that the aftershock sequence of this event at shallow depths(less than 20 km) within the coastal accretionary prism has a striking feature in the form of the earthquakeshaving a normal-fault mechanism, which are untypical of the subduction zones. These earthquakes make upabout 70% of the total number of the aftershocks. It is hypothesized that the existence of aftershocks with anormal-fault type of focal mechanism at shallow depths within the accretionary prism is associated with thedetails in the internal structure of the prism and with the thickness of weak terrigenous sediments sucked intothe interplate space by the subduction of the lithospheric plates. These details determine the observed patternof relaxation of the accumulated tectonic stresses from a wide vicinity of the prism into a compact region oftheir almost complete release during the intense coseismic slip.
- Добавил в систему: Лукк Альберт Артурович