Science Links Japan | Strong Ground Motion Simulation and Source Modeling of the Kagoshima-ken Hokuseibu Earthquakes of March 26(MJMA 6.5) and May 13(MJMA 6.3), 1997, Using Empirical Green's Function Method.

Strong Ground Motion Simulation and Source Modeling of the Kagoshima-ken Hokuseibu Earthquakes of March 26(MJMA 6.5) and May 13(MJMA 6.3), 1997, Using Empirical Green's Function Method.

Accession number;99A0456262

Title;Strong Ground Motion Simulation and Source Modeling of the Kagoshima-ken Hokuseibu Earthquakes of March 26(MJMA 6.5) and May 13(MJMA 6.3), 1997, Using Empirical Green's Function Method.

Author; MIYAKE HIROE (Disaster Prev. Res. Inst., Kyoto Univ.) IWATA TOMOTAKA (Disaster Prev. Res. Inst., Kyoto Univ.) IRIKURA KOJIRO (Disaster Prev. Res. Inst., Kyoto Univ.)

Journal Title;Journal of the Seismological Society of Japan. Second Series

Journal Code:G0931A

ISSN:0037-1114

VOL.51;NO.4;PAGE.431-442(1999)

Figure&Table&Reference;FIG.12, TBL.3, REF.22

Pub. Country;Japan

Language;Japanese

Abstract;In 1997, two magnitude 6 class earthquakes occurred in the northwestern part of Kagoshima prefecture in Japan. One of them occurred on March 26(MJMA 6.5) and the other on May 13(MJMA 6.3). We examined the source models of these two events using the observed seismograms by K-NET at four stations surrounding the source areas. We proposed an objective estimation method to obtain the parameters N and C which are needed for the empirical Green's function method by IRIKURA(1986). This method, we call source spectral ratio fitting method, gives estimates of seismic moment ratio between a large and a small event and their corner frequencies by fitting the observed source spectral ratio with the ratio of source spectra which obeys the .OMEGA.-2 model. This method has an advantage of removing site effects in evaluating the parameters. The best source model of the March mainshock was estimated by comparing the observed waveforms with synthetics using empirical Green's function method. The size of the asperity is about 7km length in the E-W direction by 6km width in the dip direction. The rupture started at the eastern-bottom of the asperity(8.2km) and extended radially to the western-upper direction. We noticed that the source model with additional small asperity to the eastern extension of major asperity improved the waveform fitting of the east-side station. In case of the May event, the aftershock distribution is 'L' shaped, and the mainshock waveforms on the rock site are composed of two clear pulses. The hypocenter of the mainshock is located close to the bottom(7.7km deep) of the intersection of the 'L' shape. Therefore, we considered two fault planes, the N-S plane and the E-W plane. The seismic moments of the two pulses were estimated nearly the same. We tested which fault plane ruptured first by comparing the initial part of the observed seismograms with synthetics.... (author abst.)

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