The Aleatory Variability of Response Spectrum Amplitude Near the Seismic Source Based on a Single-Site Ground Motion Model for Crustal Earthquakes in Japan

Abstract

Since future earthquakes inherently contain uncertainty, it is important to appropriately incorporate this uncertainty into evaluations to improve the accuracy of seismic motion evaluation. While there are many previous studies on the aleatory variability of seismic motion, there are some issues such as the limited number of observational records near seismic sources for large-scale earthquakes, which means that aleatory variability near seismic sources and its dependency on various indicators have not been sufficiently discussed. Given the increasing diversity of seismic sources considered in seismic design today, it is also necessary to evaluate the aleatory variability considering the geometric relationship between the source fault and the target site. In this study, we focused on the source areas of relatively large crustal earthquakes that occurred in Japan. We evaluated the aleatory variability from the residuals between predicted values using a Site-specific ground motion model for a single site and observed values, confirmed the spatial distribution, and discussed dependencies on source distance, period, and slip type. The findings revealed that aleatory variability is larger closer to the seismic source, larger for shorter periods, and shows different trends depending on the fault type. These insights contribute to improving the accuracy of seismic motion evaluation.