The most common cause of earthquake-related fires is broken gas lines.
About Natural Gas Earthquake Shut-off Valves
A natural gas earthquake shut-off valve automatically shuts off your gas service when an earthquake of a sufficient magnitude occurs at your home's location. After the quake has stopped and you have determined that it is safe to do so, follow the manufacturer's instructions for restoring your gas service. You will need to make sure no gas leaks exist and re-light your pilot lights. You must ensure that your appliances are safe before operating them. Your local service company can restore your gas service, but it may take many days or even weeks before someone can come to your location in a major emergency. Some companies also charge a fee to reset valves and re-light pilot lights.