One of the causes of fire during the Great Hanshin Earthquake was gas leakage.
The gas company has a microcomputer set to all the houses, to stop the gas when the earthquake intensity is 5. But the main gas valve should be closed when the earthquake is strong, just in case.
For description of the intensity, please see: http://www.kishou.go.jp/know/shindo/shindokai.html
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