5:15 PM - 6:45 PM
[U15-P91] Investigation of topographic changes associated with the 2024 Noto Peninsula earthquake using affordable mobile LiDAR and CLAS-GNSS
Keywords:2024 Noto Peninsula earthquake, mobile LiDAR, CLAS-GNSS, coastal uplift, surface deformation
1. Introduction
The distribution and the amount of displacement of topographic changes are recorded using simple measuring instruments (e.g., tape measure, box scale, and handheld GNSS) in field surveys when a disaster occurs associated with topographic change. It is also usual to use UAV-SfM and UAV-LiDAR to capture topographic changes over a wide area (Uchiyama et al., 2014; Iwasa et al., 2020). However, there are many barriers to using drones, such as regulations and airspace restrictions just after a disaster in Japan.
Recently, low-cost and lightweight handheld mobile LiDAR has become applicable to wide-area measurements (Iwasa et al., 2022). In addition, CLAS-compatible GNSS receivers, which are low-cost and capable of centimeter-level positioning on their own, have become widely available, making it easier to perform high-precision GNSS surveying (CLAS-GNSS surveying) (Namie and Kubo, 2021). These devices will enable the easy acquisition of highly accurate and wide-area data just after a disaster. The 2024 Noto Peninsula earthquake occurred on January 1, 2024, causing topographic changes in various areas, including remarkable coastal uplift mainly along the northern coast of the Noto Peninsula and surface deformation in inland areas (Yoshida, 2024; Fukushima et al., 2024). In this study, we report the characteristics of coastal uplift and land surface displacement based on measurements using mobile LiDAR and CLAS-GNSS surveying.
2. Materials and methods
To measure the amount of coastal uplift along the northern coast of the Noto Peninsula, we conducted CLAS-GNSS surveys at nine sites using a CLAS-GNSS receiver combined with several modules (M5F9P and M5D9C from Geosense and Basic from M5Stack). The amount of coastal uplift was determined by differential analysis of the CLAS-GNSS elevation values and the pre-earthquake 1-m-grid digital elevation model (DEM).
We acquired point cloud data using mobile LiDAR (Avia from Livox) and generated 10-cm-grid DEM to measure the surface deformation along the Wakayama River. The amount of surface deformation was obtained by differential analysis of the 10-cm-grid DEM and the 1-m-grid DEM.
3. Coastal uplift on the northern coast of the Noto Peninsula
The coastal uplift was largest on the northwest coast of the Noto Peninsula, 3.9 m at the Minazuki and Igisu ports and 3.8 m at the Kaiso port. On the north coast, from west to east, these were 2.6 m at the Kami-Ozawa port, 1.2 m at Shiroyone-Senmaida, 2 m at the Otani port, 1.7 m at the Otani-Higashi port, and 1.6 m at the Takaya port. On the west coast, it was 0.5 m at the Sasanami port. The values in this study were consistent with those measured by sessile organism in the field.
4. Surface deformation along the Wakayama River
A continuous south-up scarp was recognized for approximately 700 m. The strike of the scarp is northeast-southwest on the west side and east-southeast-west-northwest on the east side. The amount of displacement is largest on the west side, about 1.9 m, and smaller on the east side. On the south (uplifted) side of the scarp, a north-facing scarplet of 0.2-0.4 m and a south-facing flexure scarp of about 1.8 m were observed in some parts. These can be interpreted as secondary deformations associated with shortening displacement. As Fukushima et al. (2024) indicated, this is the tip of a large-scale slope movement that occurred as a scarp.
Funding: This work was supported by KAKENHI Grant Number JP23K18735 from the Japanese Society for the Promotion of Science and the Collaboration Research Program of IDEAS, Chubu University IDEAS202307.
The distribution and the amount of displacement of topographic changes are recorded using simple measuring instruments (e.g., tape measure, box scale, and handheld GNSS) in field surveys when a disaster occurs associated with topographic change. It is also usual to use UAV-SfM and UAV-LiDAR to capture topographic changes over a wide area (Uchiyama et al., 2014; Iwasa et al., 2020). However, there are many barriers to using drones, such as regulations and airspace restrictions just after a disaster in Japan.
Recently, low-cost and lightweight handheld mobile LiDAR has become applicable to wide-area measurements (Iwasa et al., 2022). In addition, CLAS-compatible GNSS receivers, which are low-cost and capable of centimeter-level positioning on their own, have become widely available, making it easier to perform high-precision GNSS surveying (CLAS-GNSS surveying) (Namie and Kubo, 2021). These devices will enable the easy acquisition of highly accurate and wide-area data just after a disaster. The 2024 Noto Peninsula earthquake occurred on January 1, 2024, causing topographic changes in various areas, including remarkable coastal uplift mainly along the northern coast of the Noto Peninsula and surface deformation in inland areas (Yoshida, 2024; Fukushima et al., 2024). In this study, we report the characteristics of coastal uplift and land surface displacement based on measurements using mobile LiDAR and CLAS-GNSS surveying.
2. Materials and methods
To measure the amount of coastal uplift along the northern coast of the Noto Peninsula, we conducted CLAS-GNSS surveys at nine sites using a CLAS-GNSS receiver combined with several modules (M5F9P and M5D9C from Geosense and Basic from M5Stack). The amount of coastal uplift was determined by differential analysis of the CLAS-GNSS elevation values and the pre-earthquake 1-m-grid digital elevation model (DEM).
We acquired point cloud data using mobile LiDAR (Avia from Livox) and generated 10-cm-grid DEM to measure the surface deformation along the Wakayama River. The amount of surface deformation was obtained by differential analysis of the 10-cm-grid DEM and the 1-m-grid DEM.
3. Coastal uplift on the northern coast of the Noto Peninsula
The coastal uplift was largest on the northwest coast of the Noto Peninsula, 3.9 m at the Minazuki and Igisu ports and 3.8 m at the Kaiso port. On the north coast, from west to east, these were 2.6 m at the Kami-Ozawa port, 1.2 m at Shiroyone-Senmaida, 2 m at the Otani port, 1.7 m at the Otani-Higashi port, and 1.6 m at the Takaya port. On the west coast, it was 0.5 m at the Sasanami port. The values in this study were consistent with those measured by sessile organism in the field.
4. Surface deformation along the Wakayama River
A continuous south-up scarp was recognized for approximately 700 m. The strike of the scarp is northeast-southwest on the west side and east-southeast-west-northwest on the east side. The amount of displacement is largest on the west side, about 1.9 m, and smaller on the east side. On the south (uplifted) side of the scarp, a north-facing scarplet of 0.2-0.4 m and a south-facing flexure scarp of about 1.8 m were observed in some parts. These can be interpreted as secondary deformations associated with shortening displacement. As Fukushima et al. (2024) indicated, this is the tip of a large-scale slope movement that occurred as a scarp.
Funding: This work was supported by KAKENHI Grant Number JP23K18735 from the Japanese Society for the Promotion of Science and the Collaboration Research Program of IDEAS, Chubu University IDEAS202307.