5:15 PM - 6:45 PM
[U15-P92] Surface Deformation in Suzu City and Northern Shika Town, Japan, associated with the 2024 Noto Peninsula Earthquake
Keywords:The 2024 Noto Peninsula Earthquake, earthquake surface fault, surface deformation, earthquake observation
Introduction
We report field survey of surface deformations in Wakayama, Suzu city, and the northern part of Shiga Town associated with the 2024 Noto Peninsula earthquake. Also we report source distribution around the Togigawa-nangan Fault using temporal seismic observation.
Surface Deformation in Wakayama, Suzu City
In Wakayama, Suzu City, an uplift zone about 4 km long and 100-200 m wide was recognized along the Wakayama River based on analyses of digital surface models and aerial laser data before and after the earthquake (Kokusai Kogyo, 2024; Yoshida, 2024), and the results of a field survey at Wakayama, Suzu in the middle of the uplift zone were reported (Shirahama et al. 2024). We conducted field survey of the surface deformation in Wakayama, Suzu City, referring those reports in end of January and middle of February 2024.
Naka, Wakayama, Suzu City
Multiple surface deformations (fault scarp, flexure) were observed in rice paddies and roads. The surface deformations distributed east-west to east-northeast to west-southwest direction. The deformations consist of one or more fault scarps and reverse slopes behind the scarp, which are interpreted as resulted from north-south directional shortening. Lateral displacement was also observed at some fault scarps.
The maximum drop at the fault scarp was about 195 cm to the south. On the uplift side, the southward dipping continues for more than 150 m. The fault scarp continues in a straight line about 500 m long in a northeast-southwest direction crossing the winding Wakayama River at several points. On the west side of the Naka district, the fault scarp diverged, and the drop-off was smaller on the west side and vanished.
Some of the fault scarps appeared at the base of existing steep slope, and some low hills had grown by the deformation, suggesting cumulative deformation.
Munesue, Wakayama, Suzu City
In the Munesue area on the west side of Wakayama River, anticline-like deformation was recognized by deformation of rice paddies. The location of this anticline axis is almost coincident with the Okada anticline. Fresh basement rock was exposed on the riverbed of the Wakayama River.
Nobutake, Wakayama, Suzu City
An area where three linear strips of ground deformation cutting paddy fields and roads have been reported (Yoshida, 2024). In the southern most trace with 20-40 cm uplift, deflection of the footpath and bumps on the asphalt paved road were observed. Along the two traces with 10 cm uplift, road cracks and slight deflection of the ground were observed, but continuous and distinct surface deformations were difficult to find and were considered to be the detection limit of the field survey.
Surface deformation survey in the northern part of Shika Town
We surveyed the area along the Togigawa-nangan Fault in the northern part of Shiga Town, where earthquake surface faults associated with the 2024 Noto Peninsula Earthquake have been reported by Suzuki and Watanabe (2024). The surface deformations in the area can be explained by the seismic response of reclaimed land and embankments, and no earthquake surface fault were identified.
Temporary Earthquake Observations and Hypocenter Distribution in Northern Shika Town
Temporary seismic stations were set up on January 27-28, 2024, at four locations surrounding the Togigawa-nangan Fault. We determined hypocenters using our data and Hi-net data. No seismic activity extending from the Togigawa-nangan Fault was observed, while detailed investigation including velocity structure is a future issue.
We report field survey of surface deformations in Wakayama, Suzu city, and the northern part of Shiga Town associated with the 2024 Noto Peninsula earthquake. Also we report source distribution around the Togigawa-nangan Fault using temporal seismic observation.
Surface Deformation in Wakayama, Suzu City
In Wakayama, Suzu City, an uplift zone about 4 km long and 100-200 m wide was recognized along the Wakayama River based on analyses of digital surface models and aerial laser data before and after the earthquake (Kokusai Kogyo, 2024; Yoshida, 2024), and the results of a field survey at Wakayama, Suzu in the middle of the uplift zone were reported (Shirahama et al. 2024). We conducted field survey of the surface deformation in Wakayama, Suzu City, referring those reports in end of January and middle of February 2024.
Naka, Wakayama, Suzu City
Multiple surface deformations (fault scarp, flexure) were observed in rice paddies and roads. The surface deformations distributed east-west to east-northeast to west-southwest direction. The deformations consist of one or more fault scarps and reverse slopes behind the scarp, which are interpreted as resulted from north-south directional shortening. Lateral displacement was also observed at some fault scarps.
The maximum drop at the fault scarp was about 195 cm to the south. On the uplift side, the southward dipping continues for more than 150 m. The fault scarp continues in a straight line about 500 m long in a northeast-southwest direction crossing the winding Wakayama River at several points. On the west side of the Naka district, the fault scarp diverged, and the drop-off was smaller on the west side and vanished.
Some of the fault scarps appeared at the base of existing steep slope, and some low hills had grown by the deformation, suggesting cumulative deformation.
Munesue, Wakayama, Suzu City
In the Munesue area on the west side of Wakayama River, anticline-like deformation was recognized by deformation of rice paddies. The location of this anticline axis is almost coincident with the Okada anticline. Fresh basement rock was exposed on the riverbed of the Wakayama River.
Nobutake, Wakayama, Suzu City
An area where three linear strips of ground deformation cutting paddy fields and roads have been reported (Yoshida, 2024). In the southern most trace with 20-40 cm uplift, deflection of the footpath and bumps on the asphalt paved road were observed. Along the two traces with 10 cm uplift, road cracks and slight deflection of the ground were observed, but continuous and distinct surface deformations were difficult to find and were considered to be the detection limit of the field survey.
Surface deformation survey in the northern part of Shika Town
We surveyed the area along the Togigawa-nangan Fault in the northern part of Shiga Town, where earthquake surface faults associated with the 2024 Noto Peninsula Earthquake have been reported by Suzuki and Watanabe (2024). The surface deformations in the area can be explained by the seismic response of reclaimed land and embankments, and no earthquake surface fault were identified.
Temporary Earthquake Observations and Hypocenter Distribution in Northern Shika Town
Temporary seismic stations were set up on January 27-28, 2024, at four locations surrounding the Togigawa-nangan Fault. We determined hypocenters using our data and Hi-net data. No seismic activity extending from the Togigawa-nangan Fault was observed, while detailed investigation including velocity structure is a future issue.