14:45 〜 15:00
[SCG45-05] Nonplanar Fault Geometry Controls the Spatiotemporal Distributions of Slip and Surface Displacement
キーワード：動的破壊シミュレーション、3次元断層形状、地震シナリオ予測、合成開口レーダー
The growing number of evidence demonstrates the importance of the 3-dimensional fault geometry as the controlling factor of dynamic rupture processes and magnitudes of earthquakes.
The most recent example is the 2024 Mw 7.5 Noto Peninsula Earthquake, which broke through a previously documented active fault system over 150 km in the northern central Japanese Island. This fault system is characterized by geometrical complexity. It is important to understand the physical mechanism underlying the multi-fault rupture. We conduct fully dynamic rupture simulations and identify that the 3D fault geometry controls the observed rupture process and heterogeneous spatiotemporal patterns of the fault slip, seismic radiation and crustal deformation exhibiting about five meters of the maximum uplift. Aiming to examine the effect of the 3D fault geometry, we exclude the heterogeneity arising from the frictional properties. We also avoid frictional parameter tunings to fit the coseismic observations in order to test the forecastability of our simulations. The 3D nonplanar geometry model is built based on the previously documented surface fault traces, and we use the regional stress field determined by the stress tensor inversion. As a result, the dynamic rupture simulation reasonably reproduces the observed characteristics of the heterogeneous deformation patterns. We find the rupture is accelerated, and slip is increased where the fault is bent and optimally oriented to the regional stress orientations. Remarkably, the spatial distribution of surface displacement captured by the Synthetic Aperture Radar imageries is quantitatively reproduced, as characterized by two areas of large and small peaks of uplifts. In this talk, we also discuss evidence from several other large earthquakes. Our findings may contribute to increasing the forecastability of earthquake rupture scenarios.
The most recent example is the 2024 Mw 7.5 Noto Peninsula Earthquake, which broke through a previously documented active fault system over 150 km in the northern central Japanese Island. This fault system is characterized by geometrical complexity. It is important to understand the physical mechanism underlying the multi-fault rupture. We conduct fully dynamic rupture simulations and identify that the 3D fault geometry controls the observed rupture process and heterogeneous spatiotemporal patterns of the fault slip, seismic radiation and crustal deformation exhibiting about five meters of the maximum uplift. Aiming to examine the effect of the 3D fault geometry, we exclude the heterogeneity arising from the frictional properties. We also avoid frictional parameter tunings to fit the coseismic observations in order to test the forecastability of our simulations. The 3D nonplanar geometry model is built based on the previously documented surface fault traces, and we use the regional stress field determined by the stress tensor inversion. As a result, the dynamic rupture simulation reasonably reproduces the observed characteristics of the heterogeneous deformation patterns. We find the rupture is accelerated, and slip is increased where the fault is bent and optimally oriented to the regional stress orientations. Remarkably, the spatial distribution of surface displacement captured by the Synthetic Aperture Radar imageries is quantitatively reproduced, as characterized by two areas of large and small peaks of uplifts. In this talk, we also discuss evidence from several other large earthquakes. Our findings may contribute to increasing the forecastability of earthquake rupture scenarios.