17:15 〜 18:45
[U15-P47] Seismic Reflection Images of Tsunamigenic Fault in the 2024 Noto Earthquake (M7.6) Rupture Area
キーワード：Noto earthquake、tsunamigenic fault、seismic reflection、crustal structure
A large earthquake (M 7.6) with a reverse fault-type focal mechanism (Japan Meteorological Agency, 2024) occurred on the Noto Peninsula on January 1, 2024. The earthquake rupture extended northeast offshore the Noto Peninsula and produced a large tsunami, allowing us to speculate on shallow crustal movement near the seafloor due to a deep seismogenic fault. The earthquake source fault estimated from the aftershock distribution of the January 2024 earthquake (Japan Meteorological Agency, 2024) has a total length of approximately 150 km from the west coast of the Noto Peninsula to the northeast offshore the Noto Peninsula. It is inferred that part of the ~150-km-long fault, as an active submarine fault, could serve as the source of the tsunami in the northeast offshore the Noto Peninsula. However, the detailed structure and physical properties of tsunamigenic faults with a maximum slip of about 4 m (Satake, 2024), which are believed to have caused tsunamis, are still unknown.
During the R/V Hakuho-maru cruise (March 4–16, 2024), we carried out a multi-channel seismic (MCS) reflection investigation to obtain a high-resolution image of the shallow crustal structure containing the tsunamigenic faults in the 2024 Noto earthquake (M7.6) rupture area offshore the northeast coast of the Noto Peninsula. We acquired the MCS data with good quality on a total of 14 survey lines (~45 km long for each line). We used two GI guns (~12 liters) with an 18.75-meter shot interval to obtain a high-resolution image of the shallow structure of the tsunamigenic faults. We recorded the MCS data with a recording length of 5 or 6 sec and a sampling interval of 2 msec by a 1,200-m-long, 48-channel streamer with 25 m group spacing. Navigation data by Trigger Fish 2D was stored in the formats UKOOA P1/90 and P2/91. We have performed quality control on the MCS data by using the seismic processing software RadExPro. After applying UKOOA P1/90 navigation data to the MCS data for geometry setting, we performed velocity analysis using pre-conditioned CMP (common midpoint) gathers for quick normal moveout correction and carried out CMP stacking, producing a conventional CMP stacked section. Moreover, we carried out post-stack time migration using the CMP stacked data. In this talk, we will present the preliminary results of the MCS investigation during the cruise.
During the R/V Hakuho-maru cruise (March 4–16, 2024), we carried out a multi-channel seismic (MCS) reflection investigation to obtain a high-resolution image of the shallow crustal structure containing the tsunamigenic faults in the 2024 Noto earthquake (M7.6) rupture area offshore the northeast coast of the Noto Peninsula. We acquired the MCS data with good quality on a total of 14 survey lines (~45 km long for each line). We used two GI guns (~12 liters) with an 18.75-meter shot interval to obtain a high-resolution image of the shallow structure of the tsunamigenic faults. We recorded the MCS data with a recording length of 5 or 6 sec and a sampling interval of 2 msec by a 1,200-m-long, 48-channel streamer with 25 m group spacing. Navigation data by Trigger Fish 2D was stored in the formats UKOOA P1/90 and P2/91. We have performed quality control on the MCS data by using the seismic processing software RadExPro. After applying UKOOA P1/90 navigation data to the MCS data for geometry setting, we performed velocity analysis using pre-conditioned CMP (common midpoint) gathers for quick normal moveout correction and carried out CMP stacking, producing a conventional CMP stacked section. Moreover, we carried out post-stack time migration using the CMP stacked data. In this talk, we will present the preliminary results of the MCS investigation during the cruise.