Visualization of Seismic Wavefields and Strong Ground Motions Using Data from a Nationwide Strong-Motion Network and Large-Scale Computer Simulation

Following the destructive damage that resulted from the 1995 Hyogo-ken Nanbu (Kobe) earthquake (Mw 6.9), a nationwide network of 1,800 strongmotion instruments (K-NET and KiK-net networks) were deployed across Japan by the National Research Institute for Earth Science and Disaster Prevention (NIED). These networks were established to mitigate earthquake disasters by improving our understanding of regional seismic-wave propagation and site-specific amplification of ground motions in areas such as basins beneath highly populated areas. Figure 1 shows the coverage of the K-NET and KiK-net strong-motion networks in Japan; the station interval is approximately 20–25 km. Each seismic station has a three-component accelerographwith amaximumscale of 2,000 cm/s. The ground acceleration is recorded at 100 or 200 samples/s with 24-bit resolution in A/D conversion (Kinoshita, 1998; Aoi et al., 2000). These dense seismic recordings enable the direct visualization of the wave field generated during large earthquakes. Snapshots of ground motion produced by interpolation of seismic record between stations illustrating clearly the seismic wavefield radiating from the earthquake source and amplifying in deep sedimentary basin, so that it is providing important insights into the complicated seismic wavefield and the development of strong ground motions during the past and future earthquakes. Recent advances in high-performance computers, such as the Earth Simulator supercomputer constructed in 2002 at the Japan Marine Science & Technology Center (JAMSTEC), have made it possible to perform simulations of the regional-scale propagation of high-frequency seismic waves using a detailed subsurface structural model and a source-slip model for the earthquake itself. The results of such computer simulations, when coupled with seismic observations, provide an important means of understanding the detailed complexities

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