5:15 PM - 6:45 PM
[U15-P94] Ground displacement caused by the 2024 Noto Peninsula Earthquake and its characteristics: Analysis using aerial laser survey data before and after the earthquake
Keywords:The 2024 Noto Peninsula Earthquake, airborne laser survey, ground displacement, lineament, sediment transportation
The 2024 Noto Peninsula Earthquake (Mj = 7.6), which occurred on 1 January 2024, caused many slope failures, landslides and cracks in the Noto Peninsula area. In this study, the amount of ground displacement in the Noto Peninsula was calculated using topographical data analysis based on aerial laser survey data (ALS data), and its characteristics were discussed.
The pre-earthquake data consisted of ALS data from Ishikawa Prefecture and the Hokuriku Regional Development Bureau in FY2020, FY2021 and FY2022 (some data blank areas such as unmeasured areas were scattered). Post-earthquake data are ALS data measured by the Hokuriku Regional Development Bureau on 14, 17 and 31 January 2024 (only automatic filtering was carried out, and some landmarks remain in the data). The data were provisionally processed using the ground reference station in Noto, and the data were not yet adjusted using the adjustment reference point as an emergency response. The Classification and Combined Iterative Closest Point (CCICP) method was used to calculate the amount of ground displacement based on ALS data before and after the earthquake. It is an analytical method to calculate the amount of movement between two point clouds by searching for a linear or planar form composed of nearest-neighbour points with similar surrounding distribution conditions from the point cloud data of two time periods and calculating a movement vector from the linear or planar form corresponding to both, and has also been used in the analysis of the 2008 Kumamoto earthquake (e.g. Hirakawa et al. (2019)). In this study, CCICP analysis was carried out on 1250 meshes (1000 m east-west and 750 m north-south) and the representative variation of each mesh was calculated. Note that some of the data may be displayed as noise due to the presence of residual landforms and blank areas in some of the data as mentioned above.
Figure 1 shows the amount of variation based on the CCICP analysis, with the vertical direction shown in a colour-mesh diagram and the horizontal direction shown in a vector diagram. Comparison of the CCICP results with the quasi-vertical and horizontal crustal deformations (SAR analysis results) from the analysis of ALOS2 observation data by the GSI (2024) shows that the trends of the deformations are generally consistent in both the vertical and the east-west directions. As for the horizontal vectors of crustal deformation, north-west and south-west vectors are observed, as in the observation results of crustal deformation by electronic reference points, but southward vectors are seen from the centre of Wajima City to the vicinity of Anamizu Town. The direction of this vectors is thought to reflect the geological structure and requires further detailed investigation in the future. The overall trend is that the vector volume is greater along the northern coast.
The area of sediment transport was calculated from the GSI (2024) slope failure and sedimentation distribution data and analysed in relation to the amount of change. It was confirmed that although the number of occurrence points tended to increase in areas with greater ground displacement, the sediment transport area did not necessarily show a similar trend. In addition to comparing the amount of ground displacement and the area of sediment transport, it is necessary to confirm the relationship between topographical and geological conditions and the effects of earthquake ground motions in the future.
Linear surface deformations with vertical displacement have been identified in Wakayama Town, Suzu City, Ishikawa Prefecture (e.g. Shirahama et al. (2024)). We are carrying out a detailed topographic analysis of this area. A comparison of the Red Relief Image Maps before and after the earthquake shown in Fig. 2 reveals a linear distribution of surface deformations. The relationship with the surrounding topography and the detailed amount of displacement are still being analysed and will be reported at the time of poster presentation.
References
Hirakawa, Y., Takeishi, H., Funakoshi, K., and Eguchi, H. (2019) Understanding the amount of sediment transported by the 2008 Kumamoto Earthquake and subsequent rainfall in Aso Caldera. Journal of Erosion Control Society of Japan, Vol. 72, No. 2, p.14-24.
GSI (2024) Information on the 2024 Noto Peninsula Earthquake, https://www.gsi.go.jp/BOUSAI/20240101_noto_earthquake.html (viewed April 11, 2024)
Shirahama, Y., Ishiyama, T., Tateishi, R. and Yasue, K. (2024) Surface earthquake faults along the Wakayama River associated with the 2024 Noto Peninsula earthquake (M7.6) [preliminary report] https://www.eri.u-tokyo.ac.jp/news/20465/ (viewed April 11, 2024)
The pre-earthquake data consisted of ALS data from Ishikawa Prefecture and the Hokuriku Regional Development Bureau in FY2020, FY2021 and FY2022 (some data blank areas such as unmeasured areas were scattered). Post-earthquake data are ALS data measured by the Hokuriku Regional Development Bureau on 14, 17 and 31 January 2024 (only automatic filtering was carried out, and some landmarks remain in the data). The data were provisionally processed using the ground reference station in Noto, and the data were not yet adjusted using the adjustment reference point as an emergency response. The Classification and Combined Iterative Closest Point (CCICP) method was used to calculate the amount of ground displacement based on ALS data before and after the earthquake. It is an analytical method to calculate the amount of movement between two point clouds by searching for a linear or planar form composed of nearest-neighbour points with similar surrounding distribution conditions from the point cloud data of two time periods and calculating a movement vector from the linear or planar form corresponding to both, and has also been used in the analysis of the 2008 Kumamoto earthquake (e.g. Hirakawa et al. (2019)). In this study, CCICP analysis was carried out on 1250 meshes (1000 m east-west and 750 m north-south) and the representative variation of each mesh was calculated. Note that some of the data may be displayed as noise due to the presence of residual landforms and blank areas in some of the data as mentioned above.
Figure 1 shows the amount of variation based on the CCICP analysis, with the vertical direction shown in a colour-mesh diagram and the horizontal direction shown in a vector diagram. Comparison of the CCICP results with the quasi-vertical and horizontal crustal deformations (SAR analysis results) from the analysis of ALOS2 observation data by the GSI (2024) shows that the trends of the deformations are generally consistent in both the vertical and the east-west directions. As for the horizontal vectors of crustal deformation, north-west and south-west vectors are observed, as in the observation results of crustal deformation by electronic reference points, but southward vectors are seen from the centre of Wajima City to the vicinity of Anamizu Town. The direction of this vectors is thought to reflect the geological structure and requires further detailed investigation in the future. The overall trend is that the vector volume is greater along the northern coast.
The area of sediment transport was calculated from the GSI (2024) slope failure and sedimentation distribution data and analysed in relation to the amount of change. It was confirmed that although the number of occurrence points tended to increase in areas with greater ground displacement, the sediment transport area did not necessarily show a similar trend. In addition to comparing the amount of ground displacement and the area of sediment transport, it is necessary to confirm the relationship between topographical and geological conditions and the effects of earthquake ground motions in the future.
Linear surface deformations with vertical displacement have been identified in Wakayama Town, Suzu City, Ishikawa Prefecture (e.g. Shirahama et al. (2024)). We are carrying out a detailed topographic analysis of this area. A comparison of the Red Relief Image Maps before and after the earthquake shown in Fig. 2 reveals a linear distribution of surface deformations. The relationship with the surrounding topography and the detailed amount of displacement are still being analysed and will be reported at the time of poster presentation.
References
Hirakawa, Y., Takeishi, H., Funakoshi, K., and Eguchi, H. (2019) Understanding the amount of sediment transported by the 2008 Kumamoto Earthquake and subsequent rainfall in Aso Caldera. Journal of Erosion Control Society of Japan, Vol. 72, No. 2, p.14-24.
GSI (2024) Information on the 2024 Noto Peninsula Earthquake, https://www.gsi.go.jp/BOUSAI/20240101_noto_earthquake.html (viewed April 11, 2024)
Shirahama, Y., Ishiyama, T., Tateishi, R. and Yasue, K. (2024) Surface earthquake faults along the Wakayama River associated with the 2024 Noto Peninsula earthquake (M7.6) [preliminary report] https://www.eri.u-tokyo.ac.jp/news/20465/ (viewed April 11, 2024)