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Characteristics of S wave attenuation field in rupture zones of two large earthquakes in South Asia and their relation to seismicity

Authors: Копничев Юрий Федорович, Соколова Инна Николаевна

Keywords: сейсмичность, землетрясение, литосфера, афтершок

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The characteristics of short-period shear wave attenuation and seismicity fields in rupture zones of two large earthquakes in South Asia (Kashmir, 08/10/2005, Mw 7.6 and Bhuj, 26/01/2001, Mw 7.7) are being studied. The authors used a method, based on an analysis of Sn and Pn waves amplitude ratio (by recordings of AAK-Kyrgyzstan and NIL-Pakistan seismic stations). It was shown, that strong and weak S wave attenuation is observed correspondingly in rupture zones of the interplate Kashmir and intraplate Bhuj earthquakes. Ring-shaped seismicity structure had been formed prior to the Kashmir earthquake (in contrast to the Bhuj event). Besides, several more aftershocks with M≥5.0 were recorded after the Kashmir earthquake in comparison to the Bhuj one. It is supposed, that big variations of attenuation and seismicity fields structure are connected with sharp difference of deep fluid content in the lithosphere of two rupture zones.