Coseismic slip model and early post-seismic deformation processes of the 2024 M7.5 Noto Peninsula, Japan earthquake revealed by InSAR and GPS observations

SUMMARY On 2024 January 1, an Mw7.5 earthquake ruptured the shallow reverse fault in the Noto Peninsula, which provides opportunities to better constrain the distributed coseismic slip of this earthquake and explore the early post-seismic deformation processes following this earthquake. We first utilized the coseismic displacements to invert the preferred coseismic rupture, including the optimal fault geometry and slip distribution. Our results indicated that the distributed slip mode on the simple fault plane with the dip and strike angles of 35o and 51o of this event is mainly featured by thrust slip. Three main rupture zones with ∼100 km length and 0–20 km depths have averaged slip of ∼3 m and maximum slip of ∼5.2 m, which has a seismic moment of 2.18 × 1020 Nm (Mw7.49). We first estimate the 3-D surface deformation due to the viscoelastic relaxation in the lower crust and upper mantle through the finite-element simulation method, and obtain the residual displacements at these GPS stations through removing its deformation effects from the observed post-seismic displacements. Based on the above fault geometry, we then inverted the first 138-day afterslip evolution following this earthquake by fitting the above residual displacements. The afterslip model mainly occurred the gap between two shallow slip asperities, which has a peak slip of up to ∼1.2 m and a seismic moment of 2.36 × 1019 Nm (Mw6.85). A number of aftershocks mainly ruptured on the surroundings of the coseismic slip and afterslip zones, suggesting that the aftershocks are mostly driven by the combined stress changes from the coseismic and post-seismic slip of the fault. The viscoelastic relaxation in the lower crust and upper mantle and the afterslips of the fault play the dominant roles in the early deformation processes, which also contribute to the post-seismic surface deformation following this earthquake. We simulate the deformation due to the poroelastic rebound in the top of upper crust. Model results indicate that the poroelastic rebound produces the centimetre-scale surface subsidence in the near-field area within ∼50 km around the hypocentre of the earthquake.