11:15 AM - 11:30 AM
[S04-2-03] Is the survival rate a clue to estimate the location of epicenter of historical earthquakes?
1 Introduction
I took reflectively refuge during the preliminary tremors of the 2011 off the Pacific coast of Tohoku Earthquake. This experience suggested the human beings attempt to escape from house collapsing during the preliminary tremors, and duration of preliminary tremors (i.e. epicentral distance) and survival rate would have close relationship. I try to estimate the epicenter of inland earthquakes from mortality.
2 Case of the 1858 Hietsu Eq.
This earthquake occurred midnight, was double earthquake. Local governments described victims and population, number of fallen and total houses in each village. The mortality is high along the western part of the Atotsugawa fault, and nobody injured in the Shogawa valley. The ratio of fallen houses is almost homogeneous along the Atotsugawa fault and in the Shogawa valley. These facts can be interpreted that the epicenter was at the western part of the Atotsugawa fault, and later shock occurred in the Shogawa valley. The reason why is the residents in the Shogawa valley escaped from houses at the first event, thereafter the later event caused collapse of houses, and many people had enough time to escape from collapsing houses along the eastern part of the 70 km long Atotsugawa fault.
3 Case of the 1995 Hyogo-ken Nanbu Eq. This present earthquake hit a megalopolis. The mortality was closely similar distribution of the fallen buildings rate, and victims concentrated along the basin edge. The mortality has a little relationship with the epicentral distance. This fact would reflect following situations. 1) Many people could not escape from two-storied low resistant houses. 2) Many people were killed by collapsing buildings which blocked vacant grounds. 3) People have studied “Crawl under desks while shaking". The factor 2) is common in urban area in historical age. It must be cautious to make use of survival rate to be an indicator of epicentral distance for historical earthquake in urban area.
I took reflectively refuge during the preliminary tremors of the 2011 off the Pacific coast of Tohoku Earthquake. This experience suggested the human beings attempt to escape from house collapsing during the preliminary tremors, and duration of preliminary tremors (i.e. epicentral distance) and survival rate would have close relationship. I try to estimate the epicenter of inland earthquakes from mortality.
2 Case of the 1858 Hietsu Eq.
This earthquake occurred midnight, was double earthquake. Local governments described victims and population, number of fallen and total houses in each village. The mortality is high along the western part of the Atotsugawa fault, and nobody injured in the Shogawa valley. The ratio of fallen houses is almost homogeneous along the Atotsugawa fault and in the Shogawa valley. These facts can be interpreted that the epicenter was at the western part of the Atotsugawa fault, and later shock occurred in the Shogawa valley. The reason why is the residents in the Shogawa valley escaped from houses at the first event, thereafter the later event caused collapse of houses, and many people had enough time to escape from collapsing houses along the eastern part of the 70 km long Atotsugawa fault.
3 Case of the 1995 Hyogo-ken Nanbu Eq. This present earthquake hit a megalopolis. The mortality was closely similar distribution of the fallen buildings rate, and victims concentrated along the basin edge. The mortality has a little relationship with the epicentral distance. This fact would reflect following situations. 1) Many people could not escape from two-storied low resistant houses. 2) Many people were killed by collapsing buildings which blocked vacant grounds. 3) People have studied “Crawl under desks while shaking". The factor 2) is common in urban area in historical age. It must be cautious to make use of survival rate to be an indicator of epicentral distance for historical earthquake in urban area.