2:50 PM - 3:05 PM
[HDS08-06] Policy for creating a liquefaction trend map based on geomorphologic classification for recognition of regional liquefaction risk
Keywords:liquefaction trend map, geomorphologic classification, liquefaction hazard map
1. Introduction
Ministry of Land, Infrastructure, Transport and Tourism conducted the General Technology Development Project "Study on liquefaction hazard map creation method for risk communication" in order to promote pre-disaster prevention of liquefaction and reduce its damage from FY2018 to 2020. In order to reduce the damage caused by liquefaction, residents/businesses and the government have a common understanding of the tendency of liquefaction in the area. It is important to think together about the necessity, i.e., to take risk communication.
As the first step in risk communication, in order to confirm and share the liquefaction occurrence tendency of the area between residents/businesses and the government, it is necessary information for understanding the tendency of liquefaction in the area. As the information, the "liquefaction trend map" that evaluates and classifies the liquefaction occurrence tendency for each geomorphologic classification based on the relationship between the liquefied points and the geomorphology in the past earthquakes is effective. In this presentation, we report on the policy for creating this "liquefaction trend map".
2. Basic policy and creation procedure of "Liquefaction trend map"
The "liquefaction trend map" is created based on information such as geomorphologic classification as a material showing the liquefaction occurrence tendency of the target area. In the map, the liquefaction occurrence tendency of the target area is evaluated and classified in 5 stages based on the geomorphology, man-made land, and the occurrence history of liquefaction in past earthquakes. The map scale is about 1:25,000 or larger, and the shape and distribution of geomorphology and man-made land are shown by polygon data.
The creating procedure of the "liquefaction trend map" is as follows. (1) Collection of materials, (2) Creation of geomorphologic classification maps, etc., (3) Evaluation/classification of liquefaction occurrence tendency, (4) Creation of “liquefaction trend map”.
3. Key points when creating "Liquefaction trend map"
(1) Collection of materials
- It collects previous geomorphologic classification maps, aerial photographs, old maps, man-made land creation materials, materials related to past liquefaction occurrence history, and ground information such as borehole data.
(2) Creation of geomorphologic classification maps, etc.
1) Creation of geomorphologic classification map by topography interpretation
- If there is no geomorphologic classification map, the map must be created by topography interpretation using topographic maps, DEMs, aerial photographs, etc.
- If there is a previous geomorphologic classification map, it may be possible to simplify the creation of the map by referring to them.
2) Extraction and arrangement of man-made land
- With reference to old maps, aerial photographs, and construction materials, the area of reclaimed land in the water, backfills land after gravel collection, etc. is extracted as much as possible.
3) Arrangement of liquefaction occurrence history in past earthquakes
- The history of liquefaction in the target area is organized based on books, research papers, and materials.
(3) Evaluation/classification of liquefaction occurrence tendency
- Based on the geomorphologic classification map and the information of man-made land created in above (2), the liquefaction occurrence tendency is evaluated and classified using the five stages evaluation criteria shown in Table 1.
(4) Creation of “liquefaction trend map”
- Based on the evaluation result of the liquefaction occurrence tendency in above (3), “Liquefaction trend map” as map information is created at a scale of about 1:25,000.
4. Summary
The "liquefaction trend map" reported in this presentation will be posted as map information of the liquefaction hazard map and will be used together with other disaster learning information.
Ministry of Land, Infrastructure, Transport and Tourism conducted the General Technology Development Project "Study on liquefaction hazard map creation method for risk communication" in order to promote pre-disaster prevention of liquefaction and reduce its damage from FY2018 to 2020. In order to reduce the damage caused by liquefaction, residents/businesses and the government have a common understanding of the tendency of liquefaction in the area. It is important to think together about the necessity, i.e., to take risk communication.
As the first step in risk communication, in order to confirm and share the liquefaction occurrence tendency of the area between residents/businesses and the government, it is necessary information for understanding the tendency of liquefaction in the area. As the information, the "liquefaction trend map" that evaluates and classifies the liquefaction occurrence tendency for each geomorphologic classification based on the relationship between the liquefied points and the geomorphology in the past earthquakes is effective. In this presentation, we report on the policy for creating this "liquefaction trend map".
2. Basic policy and creation procedure of "Liquefaction trend map"
The "liquefaction trend map" is created based on information such as geomorphologic classification as a material showing the liquefaction occurrence tendency of the target area. In the map, the liquefaction occurrence tendency of the target area is evaluated and classified in 5 stages based on the geomorphology, man-made land, and the occurrence history of liquefaction in past earthquakes. The map scale is about 1:25,000 or larger, and the shape and distribution of geomorphology and man-made land are shown by polygon data.
The creating procedure of the "liquefaction trend map" is as follows. (1) Collection of materials, (2) Creation of geomorphologic classification maps, etc., (3) Evaluation/classification of liquefaction occurrence tendency, (4) Creation of “liquefaction trend map”.
3. Key points when creating "Liquefaction trend map"
(1) Collection of materials
- It collects previous geomorphologic classification maps, aerial photographs, old maps, man-made land creation materials, materials related to past liquefaction occurrence history, and ground information such as borehole data.
(2) Creation of geomorphologic classification maps, etc.
1) Creation of geomorphologic classification map by topography interpretation
- If there is no geomorphologic classification map, the map must be created by topography interpretation using topographic maps, DEMs, aerial photographs, etc.
- If there is a previous geomorphologic classification map, it may be possible to simplify the creation of the map by referring to them.
2) Extraction and arrangement of man-made land
- With reference to old maps, aerial photographs, and construction materials, the area of reclaimed land in the water, backfills land after gravel collection, etc. is extracted as much as possible.
3) Arrangement of liquefaction occurrence history in past earthquakes
- The history of liquefaction in the target area is organized based on books, research papers, and materials.
(3) Evaluation/classification of liquefaction occurrence tendency
- Based on the geomorphologic classification map and the information of man-made land created in above (2), the liquefaction occurrence tendency is evaluated and classified using the five stages evaluation criteria shown in Table 1.
(4) Creation of “liquefaction trend map”
- Based on the evaluation result of the liquefaction occurrence tendency in above (3), “Liquefaction trend map” as map information is created at a scale of about 1:25,000.
4. Summary
The "liquefaction trend map" reported in this presentation will be posted as map information of the liquefaction hazard map and will be used together with other disaster learning information.