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Evidence of a deep slow event before the M w 6.6 Tottori earthquake using shear wave splitting measurements
Author(s) -
Volti Theodora,
Kaneda Yoshiyuki
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2005gl025031
Subject(s) - foreshock , seismology , aftershock , intraplate earthquake , geology , epicenter , clockwise , shear (geology) , geophysics , tectonics , physics , amplitude , petrology , quantum mechanics
Shear‐wave splitting (SWS) data, based on observations nine months before and three months after the 6th October 2000 Tottori earthquake (Chugoku, Japan) have been analyzed in order to assess the stress distribution in that area. Seismic stations are distributed within a radius of 50–100 km from the main shock epicenter. Fast polarizations agree with the regional E‐W compressive stress of the area. An apparent switch in polarizations from E‐W to N‐S occurs a few months before the main shock in the isolated area of deep foreshocks, whereas polarizations of aftershocks strike NW‐SE and rotate anticlockwise with time‐delays. We suggest that the switch of polarizations for the foreshocks is due to the occurrence of a slow slip event before the Tottori earthquake. Comparison with a tomographic study shows that foreshocks occurred in a ductile area and the “distributed shear” model for intraplate earthquakes explains best the mechanics of Tottori earthquake.