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Earth Planets Space, Vol. 57 (No. 3), pp. 185-190, 2005

LETTER

Crustal deformations in Kii peninsula associated with the SE off the Kii peninsula earthquake sequence of September 5, 2004 derived from dense GPS observations

Manabu Hashimoto, Kensuke Onoue, Fumio Ohya, Yoshinobu Hoso, Kohei Segawa, Kazutoshi Sato, and Yasuyoshi Fujita

Disaster Prevention Research Institute, Kyoto University, Uji 611-0011, Japan

(Received November 30, 2004; Revised March 4, 2005; Accepted March 5, 2005)

Abstract: We present crustal deformations in southern Kii peninsula, southwest Japan, before and after the SE off the Kii peninsula earthquake sequence of September 5, 2004, which were obtained from repeated surveys of dense GPS network. Disaster Prevention Research Institute (hereafter DPRI), Kyoto University made a reoccupation of their dense GPS network network that was occupied in February-March, 2004, right after the event to obtain crustal deformations associated with this event. Since we do not have the data just before the event, we apply an inversion of displacements of GEONET sites during the period from February-March to August, and interpolate displacements at DPRI's sites using the inverted fault model. Southward movements of about 2 cm are obtained in the middle of Kii peninsula, while displacements are rotated to southwest on the west side. These characteristics of horizontal displacement field cannot be explained only by a pure thrust faulting, but additional sources such as right-lateral faulting on a NW-SE trending fault
Key words: SE off the Kii peninsula earthquakes, GPS, crustal deformation, fault model.


Corresponding author E-mail: hasimoto@rcep.dpri.kyoto-u.ac.jp


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