9:15 AM - 9:30 AM
[SSS34-02] Reexamination of 1945 Mikawa earthquake disaster (1) Detailed distribution of earthquake victims
Keywords:Mikawa erathquake, Fukozu fault, Yokosuka fault, earthquake disaster, seismic victim, collapse rate
Iida (1978) organized the Mikawa earthquake disaster under the cooperation of Aichi prefecture, and clarify the whole picture of the disaster. However, he could not discuss the disaster in community level precisely. For example, 46% of 1200 houses were collapsed in Hukuji village, Hazu-gun in 1944 ToNankai earthquake, and additionally 67% of left 650 houses were also collapsed in 1945 Mikawa earthquakes one month later. The reason of strong damages in Hukuji is not discussed enough until now. It is very important to make clear whole picture of the earthquake disaster in history and in near future as national government. As the earthquake disaster remains a rare event, detailed research of the historical earthquake disasters needful to understand the following disasters. In the presentation, we would like to discuss the disaster of the Mikawa earthquake in local community level. 1. Discussion on characteristic disaster based on earthquake victim distribution Earthquake fault shaped S was appeared in the ground surface at the Mikawa earthquake. However recent researches of fault geomorphology and ground deformation based on geodesy point out two main faults striking with NNW-SSE direction, and an E-W striking fault is tear fault caused by slips on two faults. Additionally, dominant rupture should be occurred at Fukodu fault located in east. The total Mo estimated by ground deformation is the earthquake moment of 1.6x1019Nm(Mw6.7), and the third four of the released one is by slip of Fukodu fault. In our presentation, we discuss earthquake disaster with the local community level based on two N-S striking earthquake faults. 1) Katahara: compact cluster of dead located close to Fukodu fault Katahara town of Hoi-gun (then-9300 people and 1887 houses) located just on Fukodu fault, lose 227 people and 319 completely destroyed houses (15.2% collapse rate). In the town, the damages are different in each street corner. Numbers of dead and completely destroyed houses within the town are shown as bar charts and color scale in 59 neighborhood blocks. The dead are limited in the narrow zone of 1 km wide along the earthquake fault. There are some communities with no collapsed house, which are located 1 km distance from the fault. Dead are corresponding to 73 % of completely-destroyed houses, and some blocks closing the fault show the rate over 90%. Precisely, people are attacked by strong seismic waves during the hours of sleep, and they had no time to evacuate to outsides from houses. There are many blocks to have no dead and no collapsed houses, which are locating more 1 km far from the fault. 2) Fukuji: Decentralized dead far from fault in river plain On the one way, Fukuji village (then-673 houses), Hazu-gun locating 5 km southwestward from the Yokosuka Fault, one of main faults, lost 162-350 peoples and 400 houses completely. In one month before, the village also attacked by 1944 ToNankai earthquake, lost 21 people and 550 houses completely. They lost 1000 houses by earthquakes in 1200 houses for one month. The numbers of the dead are shown in each block in Fig.1B. The dead distributions are obviously different with that in Katahara. They lost many people in almost all blocks in the village. The collapse rate of ToNankai earthquake is by far the worst in Aichi prefecture, because, second worst is 21.3% in Tomiki village, Chita-gun. The Fukuji village is just located in river plain with Yahagi and old-Yahagi rivers. An exist of thick alluvial formation caused the large damages in Fukuji. The dead by Mikawa earthquake are caused by two reasons. One is there are very strong shaking at the blocks located immediately above the fault, and second is amplitude shaking by alluvial formation in river plain. The former is a case of Katahara and later is a case of Fukuji.