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Mechanisms of Early Postseismic Deformation Following the 2024 Noto Hanto Earthquake Inferred from GNSS Data

Description: 

The 2024 M_w 7.5 Noto earthquake provides an opportunity to investigate postseismic mechanisms in regions on and surrounding the Noto Peninsula, Japan. Here, we present our model for the early stage postseismic crustal deformation inferred from GNSS data. We consider the effects from both the viscoelastic (VE) relaxation and afterslip. We produce a postseismic velocity field up to the present (~ 2 months) by fitting each component of GNSS daily position time series with a secular velocity, amplitudes of annual and seasonal variations, steps, and a quadratic function starting from January 2nd, 2024. A calibrated VE relaxation model alone adequately explains far-field postseismic velocities but fails to predict velocities in the vicinity of the earthquake source. Another endmember model of only afterslip, derived by inverting for an optimal slip distribution on the coseismic rupture plane, tends to overpredict near-field and underpredict far-field signals, respectively. Since neither process can solely account for the data, we examine integrated VE relaxation and afterslip models. Preliminary models suggest that the postseismic velocity field can be effectively represented by a combination of afterslip and VE relaxation on a vertically layered model with a 30-40 km thick elastic layer, representing the crust and mantle lithosphere, underlain by a mantle asthenosphere with transient viscosity ~10¹⁸  Pa s. Afterslip appears to persist several 10s of km to the northeast of the Noto Peninsula, complementing the coseismic slip that appears to be restricted to the peninsula (e.g., the USGS Finite fault model). Our longer-term goals are to characterize the evolving postseismic deformation with a more comprehensive model, which may include lateral variations in viscoelastic properties, and explore the implications for postseismic stress transfer. This study provides insights into the early postseismic deformation processes following the 2024 M_w 7.5 Noto earthquake, underscoring the need to integrate both afterslip and VE relaxation to accurately capture the earthquake-induced transient deformation.

Session: The 2024 Magnitude 7.5 Earthquake and the Associated Earthquake Swarm Beneath the Noto Peninsula, Central Japan [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Jeonghyeop

Student Presenter: No

Invited Presentation: 

Authors