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[U15-P112] Complex damages associated with 2024 Noto Peninsula Earthquake in Itoigawa City, Niigata Prefecture.
Keywords:2024 Noto Peninsula Earthquake, Tsunami, Liquefaction, Itoigawa
In Itoigawa city, Niigata Prefecture, located approximately 80 km southeast from the epicenter of the 2024 Noto Peninsula Earthquake, localized and complex damages were experienced due to the earthquake. It is anticipated that the regional characteristics of these damages are attributed to the geological and topographical features of each area.
<Tsunami>
Off the coast of Naoetsu Port in Joetsu city, a maximum water level of 156 cm was recorded at 4:31 p.m. on January 1st. A fixed-point camera installed approximately 400 meters upstream from the mouth of the Sekikawa river in Joetsu city captured the phenomenon of the tsunami inundating the river around 4:35 p.m. In coastal areas of Itoigawa city, sedimentary structures and debris believed to be caused by the tsunami were observed, and a fishing boat from Suzu city, Noto Peninsula was found washed ashore on the Tozaki coast in the eastern part of Itoigawa city. The estimated maximum inundation height of the tsunami in the Joetsu region, calculated from the deposition front of washed-up debris, is approximately 2-5 m. A tendency for higher maximum inundation heights to occur on the generally shallow Naoetsu coast was observed.
<Liquefaction>
In the vicinity of Itoigawa Station, ejection of sand and uneven settlement associated with liquefaction were observed. Liquefaction-induced damages were particularly notable within an area of approximately 4,000 square meters around the south exit of Itoigawa Station. Within this area, in addition to sand ejection and uneven settlement, horizontal movements of residential buildings were also confirmed. The manifestation of fissures and uneven settlement becoming more pronounced over a period of several months was also observed. The area around Itoigawa Station, which includes the affected zone, is located in a low-lying area behind sand dunes that develop along the coast, with a high groundwater level. It is believed that liquefaction damages were induced by the sandy ground conditions and high groundwater level in this low-lying area.
<Concentrated collapse of embankments>
In the Kyogamine area located approximately 1.5 km southeast from Itoigawa Station, damages such as collapse of embankments were concentrated. The Kyogamine area, comprising approximately 200 households, was developed in 1965 and the embankments were constructed using natural river gravels in a dry-stacked structure. The significant damage to the embankments, concentrated in the central part of the residential area, was observed particularly at the boundary between the cut and fill areas, as compared to aerial photographs taken before the development of the residential area. Therefore, factors such as topographical modifications and embankment structures are considered to contribute to the concentrated embankment damage.
The damages in Itoigawa city resulting from the 2024 Noto Peninsula Earthquake exhibit localized and complex characteristics, reflecting the geological and topographical features of the region. In this presentation, we report the results of ongoing damage assessment surveys since immediately after the earthquake and discuss their relationship with geological and topographical characteristics.
<Tsunami>
Off the coast of Naoetsu Port in Joetsu city, a maximum water level of 156 cm was recorded at 4:31 p.m. on January 1st. A fixed-point camera installed approximately 400 meters upstream from the mouth of the Sekikawa river in Joetsu city captured the phenomenon of the tsunami inundating the river around 4:35 p.m. In coastal areas of Itoigawa city, sedimentary structures and debris believed to be caused by the tsunami were observed, and a fishing boat from Suzu city, Noto Peninsula was found washed ashore on the Tozaki coast in the eastern part of Itoigawa city. The estimated maximum inundation height of the tsunami in the Joetsu region, calculated from the deposition front of washed-up debris, is approximately 2-5 m. A tendency for higher maximum inundation heights to occur on the generally shallow Naoetsu coast was observed.
<Liquefaction>
In the vicinity of Itoigawa Station, ejection of sand and uneven settlement associated with liquefaction were observed. Liquefaction-induced damages were particularly notable within an area of approximately 4,000 square meters around the south exit of Itoigawa Station. Within this area, in addition to sand ejection and uneven settlement, horizontal movements of residential buildings were also confirmed. The manifestation of fissures and uneven settlement becoming more pronounced over a period of several months was also observed. The area around Itoigawa Station, which includes the affected zone, is located in a low-lying area behind sand dunes that develop along the coast, with a high groundwater level. It is believed that liquefaction damages were induced by the sandy ground conditions and high groundwater level in this low-lying area.
<Concentrated collapse of embankments>
In the Kyogamine area located approximately 1.5 km southeast from Itoigawa Station, damages such as collapse of embankments were concentrated. The Kyogamine area, comprising approximately 200 households, was developed in 1965 and the embankments were constructed using natural river gravels in a dry-stacked structure. The significant damage to the embankments, concentrated in the central part of the residential area, was observed particularly at the boundary between the cut and fill areas, as compared to aerial photographs taken before the development of the residential area. Therefore, factors such as topographical modifications and embankment structures are considered to contribute to the concentrated embankment damage.
The damages in Itoigawa city resulting from the 2024 Noto Peninsula Earthquake exhibit localized and complex characteristics, reflecting the geological and topographical features of the region. In this presentation, we report the results of ongoing damage assessment surveys since immediately after the earthquake and discuss their relationship with geological and topographical characteristics.