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Deep low‐frequency earthquakes beneath the focal region of the Mw 6.7 2000 Western Tottori earthquake
Author(s) -
Ohmi Shiro,
Obara Kazushige
Publication year - 2002
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 - 10.1029/2001gl014469
Subject(s) - seismology , geology , focal mechanism , amplitude , slow earthquake , fault (geology) , seismic wave , intraplate earthquake , geophysics , interplate earthquake , tectonics , physics , quantum mechanics
On October 6, 2000, an Mw = 6.7 crustal earthquake occurred in western Tottori prefecture, southwest Japan. Beneath the focal region of the earthquake, deep low‐frequency (DLF) earthquakes were observed at depths of around 30 km. Five DLF earthquakes were detected within 3 years before the mainshock and more than 60 DLF earthquakes were observed during the 13 months after the mainshock. We investigated the focal mechanism of the DLF earthquake that occurred 9 hours before the mainshock, using amplitude ratios of the S‐waves to the P‐waves and polarization patterns of the S‐waves. Both analyses indicated that a single‐force source mechanism is more preferable than a double‐couple source mechanism, which suggests the transport of fluid such as water or magma. This event is probably another example of DLF earthquakes that occur beneath active fault zones.