| Strong Motion Seismology Group & Strong Motion Observation Office | |
| Earthquake Research Institute, University of Tokyo | |
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Last updated: 20 August 2009 Launched: 11 August 2009 (This webpage is translated by Sum Mak from the original Japanese one.) | |
| Location of the Earthquake | |
| Ground Motions Observed by the Strong Motion Observation Office | |
| Ground Motion Attenuation | |
| Source Process (in Japanese) |
Figure 1 shows the epicenter of the Suruga Bay earthquake occurred at 05:07, 11 August 2009, the source region of the anticipated Tokai earthquake, and the depth to the top of the Philippine Sea plate. The Suruga Bay earthquake occurred at the eastern tip of the anticipated Tokai earthquake source region, at about 10km deeper than the upper boundary of the Philippine Sea plate.
Figure 1: Epicenter of the 2009 Suruga Bay earthquake (red star, determined by JMA); The source region of the anticipated Tokai earthquake (black spots, Results of the DaiDaiToku project-I based on the report of the Central Disaster Prevention Council); Depth contours of the Philippine Sea plate from DaiDaiToku project-I (blue lines, Baba et al., 2006; Sato et al., 2005).
(by Strong Motion Seismology Group)
Here shows the velocity seismograms and peak ground accelerations (PGA) observed by the Suruga Bay - Izu network, managed by Strong Motion Observation Office, Earthquake Research Institute, University of Tokyo. The waveforms cover the coast of Suruga Bay in clockwise direction, from station Omaezaki (OMZ) to station Minami-Izu (MIZ). Note that the coordinates of the surface and borehole stations at Sagara (SGR) are different.
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We studied the characteristics of the ground motions of this earthquake recorded by strong motion seismograph networks of K-NET, KiK-net, PARI, ISTL, SK-net, and ERI. Their attenutation is consistent with Si and Midorikawa's (1999) relation for in-slab earthquakes. Filter and site amplification are not applied for the measurement of PGA. A 0.1-10 Hz bandpass filter and a site amplification factor of 1.4 are used for the measurement of the engineering bedrock PGV.
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| Figure 2: Comparison of the observed PGA (upper), PGV (lower) and Si and Midorikawa's (1999) relation for in-slab earthquakes. Circle denotes the observation. Solid and dotted lines denote the average and standard deviation of the attenutation relation. | Figure 3: Comparison of the observed PGA (upper), PGV (lower) and Si and Midorikawa's (1999) relation for plate boundary earthquakes. |
(by M. Tsukagoshi, H. Miyake, and K. Koketsu)