Yuto KIMURA 

The Impact of Quantifying the Seismic Center Model on Prediction of Damaging Earthquake Ground Motions

Takaaki Ikeda

Due to being a region prone to frequent earthquakes, accurately predicting seismic motion caused by future earthquakes is crucial in our country. Efforts in seismic design of structures and disaster reduction measures by local governments involve investigating active faults and subduction zones in the surrounding areas to predict and simulate earthquakes and seismic motion that may occur in the future, using them as seismic sources. Research on earthquake motion prediction has been actively conducted since the unprecedented damage caused by the 1995 Hyogo-ken Nanbu earthquake. The development of seismic observation networks has led to enhanced observation records, revealing the heterogeneity of seismic sources and the complex seismic source rupture processes. Insights into seismic source characteristics governing distinctive seismic motion near the epicenter have also been elucidated. The Earthquake Research Promotion Headquarters has compiled and quantified these research results into a "recipe" for strong seismic motion prediction, specifically focusing on earthquakes with identified source faults.
The recipe allows for the characterization of seismic source models that can reproduce the heterogeneity of seismic sources and the seismic source rupture process, enabling high-precision prediction of strong seismic motion. However, as the recipe empirically models the relationship between earthquakes and seismic motion, considering the impact and trends of variability and uncertainty in seismic source parameters on strong ground motion is crucial. Moreover, the study only provides a conceptual approach to parameter settings, and specific methods may depend on the evaluator.
In this study, focusing on inland earthquakes where the influence of seismic source characteristics on strong ground motion is considered significant, we examined the impact of variations in parameters governing the heterogeneity of seismic sources and the seismic source rupture effect on strong ground motion through numerical analysis. Regarding seismic motion, considering the purpose of strong ground motion prediction and the potential for damage, we defined seismic motion with intensities capable of causing damage as "damage-inducing seismic motion." The main parameters under consideration were the size and location of the Strong Motion Generation Area (SMGA), the initiation point of rupture, and the rupture propagation velocity. SMGA is the location within the fault where particularly strong seismic motion is generated and serves as a parameter to evaluate the heterogeneity of the seismic source. The initiation point of rupture and rupture propagation velocity are parameters evaluating the directional effects of seismic source rupture.