HR: 13:40h
AN: S42F-01    [PDF]
TI: Seismic Shaking Maps of Osaka Sedimentary Basin, Southwest Japan (Preliminary Version)
AU: * Sekiguchi, H
EM: Haruko.Sekiguchi@aist.go.jp
AF: Active Fault Research Center GSJ/AIST, Site 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AU: Horikawa, H
EM: h.horikawa@aist.go.jp
AF: Active Fault Research Center GSJ/AIST, Site 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AU: Kase, Y
EM: kasep@ni.aist.go.jp
AF: Active Fault Research Center GSJ/AIST, Site 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AU: Ishiyama, T
EM: t-ishiyama@aist.go.jp
AF: Active Fault Research Center GSJ/AIST, Site 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AU: Satake, K
EM: kenji.satake@aist.go.jp
AF: Active Fault Research Center GSJ/AIST, Site 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AU: Sugiyama, Y
EM: sugiyama-y@aist.go.jp
AF: Active Fault Research Center GSJ/AIST, Site 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AU: Mizuno, K
EM: k4-mizuno@aist.go.jp
AF: Active Fault Research Center GSJ/AIST, Site 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AU: Pitarka, A
EM: Arben_Pitarka@URSCorp.com
AF: URS Corporation, 566 El Dorado Street, Pasadena, CA 91101 United States
AB: Active Fault Research Center, Geological Survey of Japan/AIST conducts a project of ground motion prediction in the Osaka sedimentary basin, southwest Japan, for hypothetical large earthquakes that would cause considerable damage in the future. Our ground motion prediction is characterized by a detailed 3D structure model of the Osaka sedimentary basin and rupture scenarios based on dynamic rupture simulations under constraints of geological data of active faults (Kase et al., in this meeting). A 3D Osaka basin structure model is constructed based on geological and geophysical data obtained by seismic reflection surveys, borings, and gravity measurements. The model area is 90 km in EW direction, 85 km in NS direction and down to 3 km depth. Medium constants are given in mesh data of 100 m and 50 m intervals in horizontal and vertical directions, respectively. Geometry of key sedimentary layers and basement floor, including overhang at reverse faults, are realistically expressed. Medium constants such as P- and S-wave velocities and density are given to each grid point based on empirical relations among P- and S-wave velocities, density, depositional age and depth. For active faults with enough paleoseismological information, we take the following two steps to construct rupture scenarios. First, we estimate heterogeneous slip distributions from surface displacement distributions of past earthquakes measured along an active fault. We assume that long-wavelength component of heterogeneity in rupture process is stable over geological (10e+6 yrs) time scale In the slip distribution model, slip varies along fault strike in a similar way to coseismic displacement. Along the downdip direction, it varies similar to those of source models for recent, well-analyzed earthquakes. The slip distribution thus estimated is converted into static stress change. Second, the static stress change is incorporated into dynamic rupture simulations as a variation of initial stress. Ground motion in the 3D Osaka basin structure model from the rupture scenarios is computed by the 3D finite difference method incorporating medium with S-wave velocity larger than 0.55 km/s. Response of subsurface structure shallower than engineering basement (portion with S-wave velocity lower than 0.55 km/s) is evaluated with multiple reflection theory in 1D media. For the earthquakes on active faults within the target area, we compute ground motion up to 1Hz by the 3D finite difference method with the smallest grid size of 100 m.
DE: 7209 Earthquake dynamics and mechanics
DE: 7212 Earthquake ground motions and engineering
DE: 7215 Earthquake parameters
DE: 7221 Paleoseismology
DE: 7223 Seismic hazard assessment and prediction
SC: Seismology [S]
MN: 2003 Fall Meeting