Abstract

The robustness of broadband ground‐motion simulation can promote seismic‐hazard assessment. A broadband ground‐motion simulation technique called “the recipe” is used in the scenario earthquake shaking maps of the National Seismic Hazard Maps for Japan. The recipe represents a fault rupture based on a multiple asperity model referred to as the characterized source model. Broadband ground‐motion time histories on the engineering bedrock are computed by a hybrid approach of the 3D finite‐difference method and the stochastic Green’s function method for the long‐ (>1  s) and short‐period (<1  s) ranges, respectively, using a 3D velocity structure model. The ground motion on the ground surface is computed using the 1D site response of the surface soil layers. Because the need for ground‐motion simulations of scenario earthquakes is increasing, it is important to validate the method from seismological and engineering perspectives. This study presents a validation of the recipe using velocity waveforms, peak ground velocity (PGV), seismic intensity, and pseudoacceleration response spectra. The validation scheme follows the framework of the Southern California Earthquake Center Broadband Platform. We selected two Mw 6.6 crustal earthquakes that occurred in Japan as the targets of this study: the 2000 Tottori and the 2004 Chuetsu (mid‐Niigata) earthquakes. The validation results are satisfactory except for those in the shortest‐period range (0.01–0.1 s) at large hypocentral distances (>70  km); such conditions are outside of the target range of the recipe. Simulations using a 1D velocity structure model were also examined. The simulation results for the 1D and 3D velocity structure models indicated that the 3D velocity structure models are important in reproducing PGV and the later phases with long duration, especially on deep sediment sites.

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