[S-GD01] Geodetic Advances in Crustal Dynamics and Environmental Change for Taiwan and Neighboring Regions

[SGD01-01] Strain Localization, Inelastic Deformation, and Long-term Strain Rate in Inland Japan and Their Implications for Seismic Hazard

*鷺谷 威¹、玉置 あい²、Meneses-Gutierrez Angela³ (1.名古屋大学減災連携研究センター、2.名古屋大学環境学研究科、3.防災科学技術研究所)

キーワード：長期ひずみ速度、非弾性ひずみ、GNSS、活断層

During the last few decades, dense permanent GNSS arrays have been established in many countries, enabling precise monitoring of crustal movements. Such geodetic observation is essential in evaluating seismic hazards associated with interplate and intraplate earthquakes. In such evaluations, it is important to distinguish elastic deformation due to slip deficit at the plate boundaries from slowly accumulating inelastic deformation. By comparing preseismic and postseismic deformation patterns of the 2011 Tohoku earthquake, Meneses-Gutierrez and Sagiya (2016) demonstrated the existence of persistent inelastic deformation in Japan along the localized deformation zone along the Japan Sea coast and central Japan. This inference needs verification with independent observation data. Therefore, we evaluated the long-term strain rate of inland Japan using the active fault data. We divide the Japan area into a regular grid with 10 km intervals. Then, we evaluate the strain rate for each gridded subregion based on the slip rates and the strike and dip angles of active faults that intersect the subregion. The calculated strain rate for each subregion has three horizontal strain components. Though the magnitude of the strain rate depends on the assumed grid size, it can be averaged over the surrounding area to obtain a value for comparison with other results. The averaged strain rates over northeast, central, and western Japan are consistent with those estimates in the previous study by Wesnousky et al. (1982). The spatially smoothed long-term strain rate is consistent with that based on GNSS data analysis of the inelastic strain rate, validating the geodetic approach. On the other hand, a comparison of our result with the shortening rate since the late Cenozoic indicates a systematic underestimation of the long-term strain rate in our approach. This discrepancy implies various uncertainties in the long-term strain rate, such as the duration of crustal shortening, the onset of active faulting, the contribution of buried faults, and the contribution of folding and other inelastic processes. We also discuss the hazard implications based on the long-term strain rate in the inland region.