HR: 1340h
AN: T13E-1632    [Abstracts]
TI: Imaging of P and S wave velocity structure beneath the Kii Peninsula in central Japan by combined analyses of P and S wave receiver functions
AU: * Ogawa, K
EM: ogawa@kugi.kyoto-u.ac.jp
AF: Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
AU: Hirahara, K
EM: hirahara@kugi.kyoto-u.ac.jp
AF: Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
AU: Shibutani, T
EM: shibutan@rcep.dpri.kyoto-u.ac.jp
AF: DPRI, Kyoto University, Gokasyo, Uji-city, Kyoto, 611-0011, Japan
AB: The Philippine Sea Plate (PHP) is subducting beneath the Kii Peninsula in central Japan, which generates great interplate earthquakes and low-frequency earthquakes there. It is important to closely investigate where such events occur around the PHP. Therefore we need to estimate the detailed configurations of the PHP and the Moho. Traditionally, we have so far used P wave radial receiver function (RF) to investigate S wave velocity structure by detecting P to S converted wave at seismic velocity discontinuities. In this study, we investigated P and S wave velocity structure also by detecting multiply-reflected P wave between surface and discontinuities. In the analyses, we used vertical RFs instead of auto-correlation and cross-correlation analyses. Additionally, we analyzed S wave RF of S to P and ScS to P converted waves to enhance reliability of P wave velocity structure. In this study, we used a dense seismic array that is located across the Kii Peninsula in southwest Japan from north to south. The array consists of 13 short-period seismic stations with around 5 km spacing. We used near earthquakes for detecting ScSp wave and teleseismic earthquakes for other waves. We analyzed multiply- reflected P waves by employing vertical RFs. In deconvolution, we first stacked vertical components of P waves observed at all array stations for each teleseismic event to remove local effects and improve S/N ratio. Then, we used the waveform portion with duration of 5 seconds after the P wave arrival. In addition, we analyzed Sp and ScSp waves by use of S wave RFs that are vertical components deconvolved by radial ones. In deconvolution, we used extended-time multi-taper RF estimation (Shibutani et al., 2006) instead of traditional water level methods. In the P wave RF analyses, we have investigated S wave structure by detecting Ps waves, and additionally we could investigate P wave structure by detecting multiply reflected P waves, Sp and ScSp phases. In the result of investigating P wave structure, we confirmed the phases reflected or converted at the Moho. However, we could not confirm the phase from PHP. Further newly-devised analyses would be needed to reveal the deep P and S wave structure.
DE: 7207 Core (1212, 1213, 8124)
DE: 7245 Mid-ocean ridges
SC: Tectonophysics [T]
MN: 2007 Fall Meeting