Prediction of ground motion in the Osaka sedimentary basin associated with the hypothetical Nankai earthquake

• Published in: Journal of seismology 2008-04, Vol.12 (2), p.185-195
• Main Authors: Sekiguchi, Haruko, Yoshimi, Masayuki, Horikawa, Haruo, Yoshida, Kunikazu, Kunimatsu, Sunao, Satake, Kenji
• Format: Article
• Language: English
• Subjects: Disaster management; Earth and Environmental Science; Earth Sciences; Earthquakes; Emergency preparedness; Finite difference method; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Ground motion; Hydrogeology; Original Article; Plate tectonics; Sedimentary basins; Sediments; Seismic activity; Seismology; Structural Geology; Wave velocity
• ISSN: 1383-4649; 1573-157X
• DOI: 10.1007/s10950-007-9077-8

We studied the long-period ground motions in the Osaka sedimentary basin, Japan, which contains a 1- to 3-km thickness of sediments and is the site of many buildings or construction structures with long-natural period. We simulated the broadband ground motions likely to be produced by the hypothetical Nankai earthquake: the earthquake expected to give rise to the most severe long-period ground motion within the basin. For the simulation, we constructed multiscale heterogeneous source models based on the Central Disaster Management Council of Japan (CDMC) source model and adopted a hybrid computation method in which long-period motion and short-period motion are computed using a 3-D finite difference method and the stochastic Green’s function method, respectively. In computing long-period motions, we used a 3-D structure model of the crust and the Osaka sedimentary basin. The ground motions are estimated to have peak velocities of 50–90 cm/s, prolonged durations exceeding 300 s, and long predominant periods of 5–10 s in the area with great thickness of sediments. The predominant periods are in agreement with an approximate evaluation by 4  H / V s where H and V s are the thickness of the sediment and the average S wave velocity, respectively.