Characteristic reflectors in the lower crust and uppermost mantle identified by deep seismic profiling beneath the eastern aftershock zone of the 2024 Noto Peninsula Earthquake, Japan Sea

The 2024 Noto Peninsula Earthquake ( M J 7.6) was a major crustal event with a rupture zone extending from the Noto Peninsula to the offshore region. To clarify the relationship between the seismogenic fault and the deep offshore crustal structure, we conducted a marine seismic survey across the eastern aftershock zone in August and September 2024, using a multichannel seismic reflection (MCS) system and ocean bottom seismographs (OBSs). The crustal structure directly beneath the survey line was imaged by deriving a velocity model from the acquired OBS data and applying it to prestack depth migration (PSDM) processing of the MCS data. In the sedimentary sequence, an asymmetric anticline associated with a northwest-dipping reverse fault was identified, and the location of this fault spatially corresponds to the aftershock distribution determined from OBS observations. In the crust, although no prominent reflectors were observed within the primary aftershock zone at depths of 5–15 km, three distinct reflectors (R1, R2, and R3) were detected beneath the aftershock zone at depths of 15–33 km and are interpreted to originate from the lower crust, the Moho, and the uppermost mantle, respectively. Notably, the shallowest of these deep reflectors (R1) is located at a depth of approximately 15 km, coinciding with the lower limit of the aftershock activity. This spatial correlation points to a close link between the deep crustal structures and the seismogenesis of the 2024 Noto Peninsula Earthquake.