2:45 PM - 3:00 PM
[SSS10-11] Development of Common Database for Seismic Hazard Assessment and Study on the Performance Evaluation Method
Keywords:Seismic hazard assessment, Strong-motion database, Ground-motion simulation, Ground-motion model, Performance evaluation
It is important to take into account the uncertainty of the Ground-Motion Model (GMM) in the seismic hazard assessment for huge earthquakes, or sites which are located within a few kilometers of the source fault and for which observation records are not sufficiently available. For this purpose, we have been working on the development of a strong-motion database and multiple GMMs based on the database for seismic hazard assessment.
GMMs for seismic hazard assessment in Japan can be expected to be more accurate by developing models that classify earthquake types into three categories: crustal earthquakes, subduction inter-plate earthquakes, and subduction intraplate (slab) earthquakes, which are thought to have different source and path characteristics. In the prototype version of the strong-motion database (Morikawa et al., 2020; JpGU), the types of earthquakes were classified based only on the hypocenter location and the subducting oceanic plate model. But here, we have reclassified them using the information from the mechanism solution. We classified earthquakes as subduction inter-plate earthquakes if their centroid depth, strike, and dip angle are consistent with the upper surface of the subducting plate and are of the reverse fault. The threshold values for the determination of the depth and angles were set based on the earthquakes evaluated by the Earthquake Research Committee. For earthquakes that do not apply these conditions, earthquakes whose hypocenters are shallower than the upper surface of the plate are classified as crustal earthquakes, and those with deeper hypocenters are classified as subduction intraplate earthquakes. The plate shape model is based on the 2020 version of the National Seismic Hazard Map for Japan. This reduces the uncertainty about the earthquake types in the strong-motion database.
The evaluation of the performance of the strong-motion database is useful not only for planning a policy to expand the database by using simulation data and overseas data, but also for evaluating the performance of empirical GMMs obtained from the database. In this study, we investigate a method for quantitatively evaluating the characteristics of the strong-motion database from the viewpoint of developing GMMs, which expresses the ground-motion intensity at a certain magnitude-distance as a probability distribution, as well as a method for evaluating the appropriateness of expanding the strong-motion database with simulation data. In addition, we are studying methods to evaluate the validity of expanding simulation data to the strong motion database. Based on these studies, we plan to study the quantitative performance evaluation method of GMMs.
Acknowledgments: This study is supported by the Gran-in-Aid for Scientific Research (KAKENHI Number 20H00292).
GMMs for seismic hazard assessment in Japan can be expected to be more accurate by developing models that classify earthquake types into three categories: crustal earthquakes, subduction inter-plate earthquakes, and subduction intraplate (slab) earthquakes, which are thought to have different source and path characteristics. In the prototype version of the strong-motion database (Morikawa et al., 2020; JpGU), the types of earthquakes were classified based only on the hypocenter location and the subducting oceanic plate model. But here, we have reclassified them using the information from the mechanism solution. We classified earthquakes as subduction inter-plate earthquakes if their centroid depth, strike, and dip angle are consistent with the upper surface of the subducting plate and are of the reverse fault. The threshold values for the determination of the depth and angles were set based on the earthquakes evaluated by the Earthquake Research Committee. For earthquakes that do not apply these conditions, earthquakes whose hypocenters are shallower than the upper surface of the plate are classified as crustal earthquakes, and those with deeper hypocenters are classified as subduction intraplate earthquakes. The plate shape model is based on the 2020 version of the National Seismic Hazard Map for Japan. This reduces the uncertainty about the earthquake types in the strong-motion database.
The evaluation of the performance of the strong-motion database is useful not only for planning a policy to expand the database by using simulation data and overseas data, but also for evaluating the performance of empirical GMMs obtained from the database. In this study, we investigate a method for quantitatively evaluating the characteristics of the strong-motion database from the viewpoint of developing GMMs, which expresses the ground-motion intensity at a certain magnitude-distance as a probability distribution, as well as a method for evaluating the appropriateness of expanding the strong-motion database with simulation data. In addition, we are studying methods to evaluate the validity of expanding simulation data to the strong motion database. Based on these studies, we plan to study the quantitative performance evaluation method of GMMs.
Acknowledgments: This study is supported by the Gran-in-Aid for Scientific Research (KAKENHI Number 20H00292).