[M-TT37] New Developments in Earth Science Explored by Dense GNSS Observation Networks

[MTT37-05] Dense GNSS Observation around the Western Nagaoka Plain Fault Zone: Postseismic Deformation after the 2024 Noto Peninsula Earthquake

*Takeshi Sagiya¹ (1.Disaster Mitigation Research Center, Nagoya University)

Keywords:Densified GNSS Array, Western Nagaoka Plain Fault, Inelastic deformation, 2024 Noto Peninsula Earthquake

We have been monitoring crustal deformation in the Mid-Niigata region around the Western Nagano Plain Fault Zone with a densified GNSS array composed of 20 continuous sites operated by the Association for Earthquake Prediction and Nagoya University, 30 stations by the SoftBank Corp., and the GEONET stations. We processed the raw GNSS data from 2019 to January 2025 with the Bernese GNSS software version 5.4 with the Precise Point Positioning approach with the satellite orbit, clock, and bias provided by the Center for Orbit Determination in Europe (CODE). On 1 January 2024, the Noto Peninsula Earthquake (Mw7.5) occurred, and significant coseismic displacements were observed in the study area. After the earthquake, many sites show changes in the linear trends of daily coordinates, but exponential or logarithmic transient decay is not seen in the study area. The observed postseismic deformation can be reproduced by considering a viscoelastic relaxation model with a lithosphere thickness of 35 km and an asthenosphere viscosity of 1 x 10^18 Pa s, representing the regional rheological structure. More details about spatiotemporal variations in the postseismic deformation will be discussed.

Acknowledgment
The SoftBank's GNSS observation data used in this study was provided by SoftBank Corp. and ALES Corp. through the framework of the "Consortium to utilize the SoftBank original reference sites for Earth and Space Science".