Basin and crustal velocity structure models for the simulation of strong ground motions in the Kinki area, Japan

Abstract

We constructed a prototype of the basin and crustal structure model for the Kinki area, southwest of Japan, for the simulation of strong ground motions of hypothetical crustal and subduction earthquakes. We collected results of the deep seismic velocity profiles obtained by the reflection experiments and seismic imaging results, which were conducted in the Kinki area. The obtained profiles give underground velocity structures of the crust, from the surface to the subducting slab. We also gather the basin velocity structure information of the Osaka, Kyoto, Nara, and Ohmi basins. To examine the applicability of the constructed velocity structure model to the ground motion simulation, we simulated waveforms of an intermediate size event occurred near the source area of the hypothetical subduction earthquakes. Simulated ground motions using the basin and crustal velocity structure model are fairly well reproducing the observations at most of stations, and the constructed basin and crustal velocity structure model is applicable for the long-period ground motion simulations.

Surface wave group velocity in the Osaka sedimentary basin, Japan, estimated using ambient noise cross-correlation functions

“…This result validates the present velocity structure model in this area. The current UMC2013 model showed better performance than the previous model of Iwata et al (2008).…”

“…Figure 12 shows examples for three cells. The theoretical dispersion curves calculated from the previous model (Iwata et al 2008), which was constructed by a different approach of modeling, are also presented in this figure for comparison. For cells (5, 6) and (8, 4), the estimated group velocities in the period range of 1.5-8 s were in good agreement with the theoretical dispersion curves of the fundamental mode of the Love and Rayleigh waves.…”

“…The velocity structure of the Osaka basin has been investigated extensively using geophysical and geological techniques such as gravity anomaly measurements (e.g., Nakagawa et al 1991;Inoue et al 1998), refraction and reflection surveys (e.g., Toriumi et al 1990; Kagawa et al 1990;Horike et al 1996), offshore seismic air gun reflection surveys (e.g., Iwasaki et al 1994;Iwabuchi et al 2000;Ito et al 2001), boring explorations (e.g., Ikebe et al 1970;Yoshikawa et al 1998;Inoue et al 2013), microtremor measurements (e.g., Kagawa et al 1998;Uebayashi 2003;Yoshimi 2012;Minami et al 2014), and strong motion observations (e.g., Hatayama et al 1995;Toki et al 1995). Based on the results obtained using these techniques and ground motion simulations for observed moderate events, three-dimensional velocity structure models of the Osaka basin have Open Access *Correspondence: k-asano@egmdpri01.dpri.kyoto-u.ac.jp 1 Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan Full list of author information is available at the end of the article been developed and improved over several decades (e.g., Kagawa et al 1993Kagawa et al , 2004Horikawa et al 2003;Iwata et al 2008;Iwaki and Iwata 2011;Sekiguchi et al 2013). Although many types of surveys have been conducted, more direct information and validation on the S-wave velocity structure is still necessary to improve the velocity structure model because the available constraints from those surveys are not distributed uniformly over the basin.…”

Reproduction of microseism H/V spectral features using a three-dimensional complex topographical model of the sediment-bedrock interface in the Osaka sedimentary basin

“…Apart from this problem, for all the regions considered, the FDM simulation reproduced the HVSR extremely well, in terms of not only the fundamental peak frequency but also the spectral curves, which is sensitive to any irregularity in the subsurface structure, and the anisotropy of the amplitude of horizontal motions. Iwaki & Iwata (2010) also succeeded in reproducing the H rms VSR determined from observations, though the number of seismic observation sites was limited, by simulating the seismic motions of the coda portion using a model of the Osaka sedimentary basin (Iwata et al . 2008) which is different from the one employed in this study.…”

Validation of 3-D basin structure models for long-period ground motion simulation in the Osaka basin, western Japan

“…They assumed that the sediment consists of three layers whose interface depths are proportional to the seismic bedrock depth. As the spline model is easily modifiable by adding new control points, they have been continuously adopting new exploration information to improve their basin velocity structure model (Kagawa et al 1993;Miyakoshi et al 1997;Miyakoshi et al 1999;Iwata et al 2006Iwata et al , 2008. Their model is extremely compact as it consists of only the spline function coefficients; however, it has a disadvantage in that the sudden lateral changes in the interfaces cannot be described.…”