Feature article

8

Feature article

Survey of fire damage caused by the 2024 Noto Peninsula Earthquake

Urban Planning Department

○ Overview

In the 2024 Noto Peninsula Earthquake that occurred on January 1, 2024, it was reported that a total of 17 fires resulting from the earthquake occurred in Niigata Prefecture, Toyama Prefecture, and Ishikawa Prefecture. Among them, remarkable damage occurred in Kawai Town, Wajima City, Ishikawa Prefecture.

The National Institute for Land and Infrastructure Management and the Building Research Institute conducted a site survey to confirm the status of damage of this fire upon request from the Housing Bureau of the Ministry of Land, Infrastructure, Transport and Tourism.

Research introduction

1. Confirmation of the range of damage and situation of firestopping by the site survey

The burnt area was identified by the site survey, and at the same time the statuses of buildings inside and outside the burnt area (building structure, earthquake damage, deformation and discoloration caused by fire) and their separation distances, road widths, and the situation of vacant land and trees were confirmed (photo).

In addition, based on the site survey and news images of news media as well as the information transmitted on the Internet by individuals such as SNS, the range of fire spread by time was estimated (Fig.-1).

〔图〕1) SNS(X,former Twitfer) message posted by Awho is considered to be a local residen2)TV Kanazawa Fixed point camera imag

Photo Examples of buildings remaining in the fire spread area

Fig.-1 Fire spread dynamics

2. Confirmation of the range of spread of sparks

In order to confirm the situation of spread of sparks during the fire, we checked the range where extinguished charcoal remained around the burnt area (Fig.-2).

Extinguished charcoal was concentrated in the northern side of the burnt area, and the size of the extinguished charcoal collected on the site was relatively larger in a nearby place located true north of the burnt area, and many relatively small and thin pieces were collected in a place far from the areas. Similarly, many relatively small pieces were collected on the northeastern side.

〔图〕Date and time osurveyJanuary 4,202408:00-10:30Range of fire spread(rough farm)Specific locatianwhere charcoalwas foundRa

Fig.-2 Situation of the spread of sparks

3. Detection of a region where a large-area fire occurred by an artificial satellite

During the occurrence of a large-scale earthquake, it is difficult to grasp the entire situation of damage, and therefore large-area observation information by means of an artificial satellite is effective. In the earthquake being considered, we tried detection of fire regions based on the observation data by means of the NASA and NOAA satellites equipped with infrared sensors (Terra, Aqua, Suomi-NPP and NOAA-20). As a result, it was confirmed in the early stage before dawn on January 2 that large-scale fires could have occurred in Kawai Town, Wajima City, Nafune Town, Wajima City and around Shiomaru, Noto Town, and such information was utilized as reference information in the implementation of the site surveys.

We also conducted a study of the detection of fire regions by means of a satellite SAR (Synthetic Aperture Radar). The satellite SAR actively irradiates radio waves that pass clouds onto the ground surface and measures the strength of the reflection, and therefore it enables observation of the ground surface at night or in a situation where there are clouds. As a result of using the images observed before and after the earthquake by the ALOS-2 satellite of JAXA in the large-scale fire region in Kawai Town, Wajima City, and applying deep learning techniques, the results of inference that nearly match the burnt area confirmed by the site survey were obtained, and the possibility of the grasping of a detailed fire range by means of the satellite SAR has been confirmed.

〔图〕1/2 01:00 (Suomi-NPP)1/2 01:54 (NOAA-20)□1/1 22:05 (Terra)1/2 02:05 (Aqua)Burnt areaBackground image: GSI Tiles(https://

Fig.-3 Results of detection of fires by means of satellite infrared data

〔图〕Background image: Pseudocolor image created byallocating the observationdata* with ALOS-2 before theearthquake (Oct. 19,

Fig.-4 Results of inference of the burnt area by means of the satellite SAR data

4. Analysis of the tendency of fire occurrence

We confirmed to what extent the frequency of occurrence of earthquake-related fires in the 2024 Noto Peninsula Earthquake was as compared with the earthquakes in the past (Fig.-5). Here, the PGV (Peak Ground Velocity: maximum ground movement speed) that is an index of the intensity of shaking with the number of fire occurrences (fire occurrence rate) per unit floor area of a building. It can be confirmed that, among the earthquakes compared, the fire occurrence rate of the 1995 Southern Hyogo Prefecture Earthquake was particularly high. It can be considered that this was related to the fact that, in the 1995 Southern Hyogo Prefecture Earthquake, toppling damage of buildings caused by shaking was especially conspicuous. Whereas, the distribution of the data points of the 2024 Noto Peninsula Earthquake was not deviated greatly from the distribution of the data points of the past earthquakes. Although there is a common point that there was a lot of toppling damage of buildings, from the viewpoint of the fire occurrence rate, we can see that the 1995 Southern Hyogo Prefecture Earthquake and the 2024 Noto Peninsula Earthquake have different features.

〔图〕插图

Fig.-5 Relationship between PGV and number of fire occurrences per unit floor area

○ Conclusion

Regarding the city area fire that occurred in Kawai Town, Wajima City on January 1, 2024, we presented the results of analysis of fire spread dynamics, analysis of artificial satellite data, and analysis of the tendency of fire occurrence as compared with the earthquakes in the past, focusing on the site survey conducted on January 4 in the same year.

We express our sincere condolences to people who suffered damage caused by the earthquake and the fires that occurred after that.

For a related article, refer to:

· Quick Report of the Field Survey on the Building Damage by The 2024 Noto Peninsula Earthquake, Technical Note of NILIM No. 1296 (P. 6-1 to P.6-27)