[U-16] 2024年能登半島地震(2:E)

[U16-P06] Effects of the 3D fault geometry, regional stresses and earthquake history on the 2024 Noto Peninsula earthquake: Insight from dynamic rupture simulations

*安藤 亮輔¹、福島 洋²、吉田 圭佑⁴、今西 和俊³ (1.東京大学大学院理学系研究科、2.東北大学災害科学国際研究所、3.産業技術総合研究所、4.東北大学理学研究科附属地震噴火予知研究観測センター)

キーワード：動的破壊シミュレーション、3次元断層形状、応力場、合成開口レーダー

The source fault of the 2024 Noto Peninsula earthquake is inferred to be located along the western and northern coast of the peninsula, consisting of previously documented multiple fault segments. This fault system presents geometrical complexity, including the bend fault off the Cape Saruyama, which marks the northwestern corner of the peninsula. We conducted the dynamic rupture simulation with the observational constraints of the 3D fault geometry and regional stress field. We have confirmed the preseismic estimates of these constraints are consistent with those of postseismic ones based on the spatial distribution and focal mechanisms of the observed aftershocks. The numerically efficient boundary integral equation method (FDP-BIEM) is employed to consider the complicated 3D fault geometry in the dynamic rupture simulation. We reasonably reproduce the overall characteristics of the coseismic slip distribution on the fault and surface displacement together with the rupture process and waveforms. The rupture is nucleated in the middle of the fault system due to the swam and the 2023 M6.5 events and then propagated southwest, followed by the arrest in the low-stress area due to the 2007 M6.9 event. To the northeast, our simulation shows that the rupture is transferred to the northwest dipping conjugate faults (F42) consisting of the northeastern part of the source faults. In particular, the simulation quantitatively reproduces the observed significant uplift concentrated around the northwestern area of the Noto peninsula, which SAR captures, without using coseismic observations. We have identified that the bend fault off the Cape Saruyama most probably caused the largest slip and uplift that occurred there. The mechanism causing the large deformations is the orientation of the fault surfaces against the principal stress axes, which is consistent with the preferred orientation with the larger shear and smaller normal tractions. We also compare the synthetic and observed strong motion waveforms and interpret the source effects.