The Kamchatka subduction zone: Seismotectonic regionalization and geodynamics |
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Authors: | G P Avdeiko A A Palueva |
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Institution: | 1.Institute of Volcanology and Seismology, Far East Division,Russian Academy of Sciences,Petropavlovsk-Kamchatskii,Russia |
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Abstract: | Seismotectonic regionalization of the Kamchatka subduction zone was carried out by retrospective analysis of the temporal
sequence and locations of earthquake occurrence and an examination of relationships between the earthquake hypocenters and
morphostructures in the continental slope of eastern Kamchatka. Ten segments separated with earthquake-generating strike-slip
faults have been identified in the overthrusting (overhanging) margin of the Sea-of-Okhotsk plate in the zone where the Pacific
and the Sea-of-Okhotsk plates interact orthogonally. Two to three earthquake-generating thrust blocks have been identified
within these segments. This type of subduction is consistent with the keyboard-block model of L.I. Lobkovskii and B.V. Baranov.
We put forward a model involving segmentation and generation of thrust blocks due to nonuniform coupling between the subducted
Pacific plate and the overhanging Sea-of-Okhotsk plate. According to this model, both segmentation and the formation of thrust
blocks are caused by nonuniform plate coupling due to unevenness in the relief of the plunging plate. The thrusts have relief
expression as underwater highs and terraces, which indicate that a tsunami-generating earthquake can occur at this location.
The highest rate of occurrence for magnitude 7 or greater earthquakes is found at the sharp bend of the Pacific plate, where
the subduction angle is 10°–12° instead of 50°–51°, corresponding to a frontal (tectonic) arc, which can be traced by a positive
free-air gravity anomaly and by an isostatic anomaly. |
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