Active tectonics, tectonic background, and thrust geometries around the source regions of the 2024 Noto Peninsula earthquake (M7.6)

The 2024 Noto Peninsula Earthquake (M7.6) on January 1, 2024 occurred beneath the northern coast of Noto peninsula, central Japan. Focal mechanism of the mainshock, geodetic and seismic observations and their analyses indicate that it was a reverse fault-type earthquake which ruptured > 150 km long. In order to identify the structural characteristics and origins of nearshore and offshore active faults in the eastern Sea of Japan, including off the Noto Peninsula and Toyama trough, we performed structural analysis on offshore and onshore-offshore multi-channel seismic profilings (MCS) obtained before the earthquake. The structural and mechanical boundaries between continental and oceanic crust near the rift axis and surrounding marginal normal faults have been the most important rift structures related to the Miocene back-arc opening in terms of seismotectonics in the Sea of Japan, as demonstrated by the Nihonkai Chubu earthquake of 1983 (M7.7). We also estimate that the eastern portion of the fault plane that caused the 2024 mainshock has a fault bend or concave up shape at a depth of about 10 km, in conjunction with coseismic deformation and aftershock distribution. The discrepancy between the thrust geometry and the spatial distribution of the former shorelines of the MIS 5 marine terraces may indicate that the tectonic uplift of the peninsula at the intermediate (~105 yrs) timescales may be caused by both the 2024 thrust fault and nearby positively reactivated rift structures beneath the Toyama trough, which are underlain by a mechanical "core" made of high-Vp lower crust probably due to mafic intrusion. In the presentation,  we also discuss the late Cenozoic tectonic background of this back-arc seismically active region based on onshore and offshore seismic geophysical data.