Nagasaka, Yosuke

Strong Ground Motion Simulation for the 2005 Central Chiba Intraslab Earthquake With the Pseudo Point-Source Model

Abstract eng:
Validated strong ground motion simulation methods are important for an earthquake-resistant design of structures. However, in the technical standards for ports in Japan, limited methods are available to evaluate shaking from intraslab earthquakes, which occur inside subducting plates. In this study, strong ground motion simulations that use the pseudo point-source model were conducted on the July 23, 2005 Central Chiba intraslab earthquake, which occurred under the Tokyo metropolitan area. The purpose is to develop a suitable strong ground motion estimation method for intraslab earthquakes. Results are analyzed to identify the applicability and understand the limitations of the model. The strong ground motion simulation showed a generally good agreement with observed records. However, underestimation of observed ground motions was found at several stations west of the epicenter. One of the possible causes is the rupture directivity effect, which the current version of the pseudo point-source model does not consider. The rupture process estimated by waveform inversion indicated that the rupture propagated toward the surface. This rupture can cause forward rupture directivity effect at the underestimated stations. We then attempted to introduce a corner frequency model that expressed the rupture directivity effect of unilateral rupture. The modelled corner frequencies do not match the observed corner frequencies. Although considering the directivity effect was unnecessary for the 2005 Central Chiba intraslab earthquake, we continued to investigate the applicability of the model. Variation in the site amplification factors is discussed as another potential cause of the underestimation. At the underestimated stations, the site amplification factors of the intraslab earthquakes that occurred near the 2005 Central Chiba earthquake were found to be larger than those of the earthquakes that occurred at various locations. The results of the simulation were improved with the use of corrected site amplification factors for intraslab earthquakes.

Contributors:

Nozu, Atsushi

Conference Title:

Proceedings of the 16th World Conference on Earthquake Engineering

Conference Title:

16th World Conference on Earthquake Engineering

Conference Venue:

Santiago (CL)

Conference Dates:

2017-01-09 / 2017-01-13

Rights:

Text je chráněný podle autorského zákona č. 121/2000 Sb.