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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy<br />

(S) - <strong>IASPEI</strong> - International Association of Seismology and Physics of the Earth's<br />

Interior<br />

JSS008 Poster presentation 2018<br />

Electrical resistivity structure around the hypocentral region of DLF events<br />

in the Kii peninsula, southwest Japan<br />

Dr. Naoto Oshiman<br />

Disaster Prevention Research Institute Kyoto University IAGA<br />

Tkehiro Nagano, Rokei Yoshimura, Satoru Yamaguchi, Makoto Uyeshima<br />

Recently, very high dense seismic observation network, called Hi-net in Japan, revealed the existence of<br />

deep low-frequency (DLF) events (or deep non-volcanic tremors) at depths of about 35km along the<br />

subductiong Philippine Sea plate, southwest Japan (Obara, 2002). Their generation mechanism has not<br />

been well understood, yet. Crustal fluids are, however, strongly thought to generate such DLF events,<br />

taking their characteristics into consideration.In order to investigate electrical resistivity structure<br />

around the hypocentral region of the DLF events, southwest , we conducted the magnetotelluric (MT)<br />

soundings in the Kii peninsula. We made wide-band MT measurements at 16 sites along the survey line<br />

of about 70 km across the epicentral area of the DLF events in the Kii peninsula, in September, 2005.<br />

Apparent resistivity and phase of the TM mode of the wide-band MT, together with those of lonerperiod<br />

MT and Network-MT measurements, were used for determining a two-dimensional resistivity<br />

structure model. In the obtained best-fit model, a low resistive region is seen at depths around the<br />

hypocenters of the DLF events located in the middle of the profile, suggesting that crustal fluids from<br />

the subducting Philippine Sea plate exist around the region.<br />

Keywords: resistivity, mt

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