[P06] Crustal structure

[P06-09] Full-Waveform Inversion Imaging of the 2024 Noto Mw 7.6 Earthquake Rupture Zone

*Hamzeh Mohammadigheymasi¹, Ehsan Jamali Hondori², Yige Yang¹, Jin-Oh Park¹ (1. Atmosphere and Ocean Research Institute, The University of Tokyo, 2. Geoscience Enterprise Inc. (GSE), Tokyo)

The January 1, 2024, Mw 7.6 earthquake that struck the Noto Peninsula, Japan, generated a destructive tsunami and caused widespread coastal damage. Marine multichannel seismic (MCS) reflection surveys conducted by the Atmosphere and Ocean Research Institute (AORI), together with high-resolution pre-stack depth-migrated (PSDM) sections, reveal a prominent large deformation zone (LDZ) within the rupture area. This ~2.5–3.8 km wide and ~30 km long LDZ comprises a complex strike-slip fault system that includes steeply southeast-dipping reverse faults (~50°–75°), several of which may have contributed to tsunami generation. However, interpretation of these structures is hampered by acquisition limitations, such as short streamer length and sparse receiver spacing, which reduce the accuracy of interval velocity estimation and, consequently, of depth imaging. To address these challenges and to place stronger constraints on the velocity structure, we conducted a full waveform inversion (FWI) study using legacy seismic data recorded by JAMSTEC in line crossing the LDZ. The raw dataset was reprocessed with an advanced depth-imaging workflow to generate initial depth-domain interval velocity models. These models were then refined using a frequency-domain FWI algorithm applied over a selected frequency band. Our preliminary results yield improved velocity models for a cross-section passing through the LDZ of the 2024 Noto earthquake, providing enhanced structural imaging and underscoring the potential for time-lapse seismic studies of subsurface changes before and after the earthquake.