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[U15-P98] Analysis of the slope failure induced by the 2024 Noto Peninsula Earthquake based on geological classification and slope direction
Keywords:2024 Noto Peninsula Earthquake, Noto Peninsula, slope failure, geological classification, slope direction
In the Noto Peninsula, Oligocene to Miocene sedimentary and volcanic rocks were mainly distributed. The NE-SW trending fold axes and faults distributed in the northeastern part of the Noto Peninsula, where the slope failures induced by the 2024 Noto Peninsula Earthquake were concentrated. Overall, the earthquake is considered to have occurred due to the fault activity of the NE–SW-trending and SE-dipping reverse faults. Vector data was published by Geological Survey of Japan (GSJ) as the Seamless Digital Geological Map of Japan (1:200,000) version 2 (hereafter, the Seamless Digital Geological Map) in throughout the peninsula and the Geological map of Japan 1:50,000 “Suzumisaki, Noto-Iida and Horyuzan District” (hereafter, the Suzumisaki Geological Map) in the northeastern part of the peninsula. Since the Suzumisaki Geological Map show more detailed geological classification and distribution than the Seamless Digital Geological Map, the respective vector data was used for the analysis. The distribution map of slope failures and depositions induced by the earthquake was published by the Geospatial Information Authority of Japan (GSI). Since the distribution map shows collapse and deposition areas together, we interpreted the collapse sites based on topographic information. The slope direction of the collapse sites was estimated using the 10 m DEM published by GSI.
From the analysis of entire Noto Peninsula using the Seamless Digital Geological Map, the results were as follows. The number of collapse sites per 1 km2 were greater in the area of the Miocene lava and volcaniclastic rocks, the Miocene gravelstones, and the Miocene siliceous mudstones than in the area of other geological classification. Thus, the relationship between the number of collapse sites and geological classification was found. The slope direction of the collapse sites was predominantly in S–SE direction, regardless of geological classification.
Based on the analysis of the northeastern part of the Noto Peninsula using the Suzumisaki Geological Map, the results were as follows. The number of collapse sites per 1 km2 were greater in the area of the Miocene volcaniclastic rocks, the Miocene lava and the Miocene mudstones than in the area of other geological classification. Thus, it is recognized that the number of collapse sites related to geologic classification. Miocene lava and volcaniclastic rocks with frequent collapses in the map were classified as Horyuzan Formation and Awagura Formation. The number of collapse sites per 1 km2 of Horyuzan Formation and Awagura Formation was greater in the area of volcaniclastic rocks than in the areas of lava. The slope direction of the collapse site was predominantly in S–SE direction, except for Awagura Formation. The strata, distributed in the map, predominantly inclined in the SSE or NNW direction. Generally, the dip direction of the strata tends to align with or opposes the slope direction of the collapse site.
As mentioned above, the collapse sites induced by the earthquake tend to be concentrated in the area of the Miocene volcaniclastic rocks. Overall, the same direction between the slope direction of the collapse sites and the dip direction of the reverse faults, which were activated during the earthquake, was predominant.
From the analysis of entire Noto Peninsula using the Seamless Digital Geological Map, the results were as follows. The number of collapse sites per 1 km2 were greater in the area of the Miocene lava and volcaniclastic rocks, the Miocene gravelstones, and the Miocene siliceous mudstones than in the area of other geological classification. Thus, the relationship between the number of collapse sites and geological classification was found. The slope direction of the collapse sites was predominantly in S–SE direction, regardless of geological classification.
Based on the analysis of the northeastern part of the Noto Peninsula using the Suzumisaki Geological Map, the results were as follows. The number of collapse sites per 1 km2 were greater in the area of the Miocene volcaniclastic rocks, the Miocene lava and the Miocene mudstones than in the area of other geological classification. Thus, it is recognized that the number of collapse sites related to geologic classification. Miocene lava and volcaniclastic rocks with frequent collapses in the map were classified as Horyuzan Formation and Awagura Formation. The number of collapse sites per 1 km2 of Horyuzan Formation and Awagura Formation was greater in the area of volcaniclastic rocks than in the areas of lava. The slope direction of the collapse site was predominantly in S–SE direction, except for Awagura Formation. The strata, distributed in the map, predominantly inclined in the SSE or NNW direction. Generally, the dip direction of the strata tends to align with or opposes the slope direction of the collapse site.
As mentioned above, the collapse sites induced by the earthquake tend to be concentrated in the area of the Miocene volcaniclastic rocks. Overall, the same direction between the slope direction of the collapse sites and the dip direction of the reverse faults, which were activated during the earthquake, was predominant.