[S-TT36] 合成開口レーダーとその応用

[STT36-P04] Using InSAR for evaluating the accuracy of earthquake location determination, Comparison of Iranian and Japanese cases

*Nematollah Ghayournajarkar¹、Yo Fukushima² (1.Graduate School of Science, Tohoku University、2.International Research Institute of Disaster Science, Tohuku University)

キーワード：InSAR, Finite rectangular fault, Earthquake location accuracy

Accurate location and extent of the earthquake rupture provide fundamental information for seismic hazard evaluation. Interferometric Synthetic Aperture Radar (InSAR) is a promising technique to constrain fault parameters because it has high spatial resolution in the epicentral area for shallow earthquakes, and the fault model derived from InSAR can be taken as the ground truth. In this study, we compared the fault location derived from InSAR to the epicenters determined by local and global seismic networks. We focused on shallow earthquakes that occurred in Iran and Japan, where the station density of the local seismic networks differs significantly, in order to evaluate how the station density and azimuthal coverage influence the accuracy of the earthquake location determination. On each of the five Iranian and five Japanese earthquakes, we obtained the coseismic interferograms, applied a Particle Swarm Optimization (PSO) method assuming a rectangular finite fault with uniform slip to obtain the optimal rupture location, and then calculated the distance between seismic-derived epicenters and InSAR-derived surface-projected fault plane for each earthquake. The results for the Iranian earthquakes showed that the distance between IRSC (Iranian Seismological Center)-derived epicenter and the fault plane was larger than that between the USGS-derived epicenter and the fault plane. Since the spatial density of the IRSC network is better than the USGS network, we can attribute the higher accuracy of the USGS epicenters to the better azimuthal coverage of the USGS network. For the case of the Japanese earthquakes, the epicenter determined by JMA (Japan Meteorological Agency), which has good azimuthal coverage and much denser spatial coverage than the USGS network, was closer to the InSAR-derived fault plane compared to the USGS epicenter. These results indicate that 1) good azimuthal coverage of the seismic network is fundamentally important in obtaining accurate epicenters, and 2) the dense station coverage leads to improving the accuracy.