Early Warning Systems for the mitigation of earthquake-related technological risks

Fumio Yamazaki
Institute of Industrial Science, The University of Tokyo, 7-22-1 Roppongi, Minato-ku,
Tokyo 106-8558, Japan.
Tel. : +81-3-3401 8142, Fax: +81-3-3408 2666,
E-mail: yamazaki@iis.u-tokyo.ac.jp

This paper highlights recent developments on early warning systems for mitigation of earthquake-related technological risks in Japan. To avoid earthquake-related secondary disasters to transportation and lifeline systems and other urban facilities, several earthquake monitoring networks have been established in order to use earthquake information for early warning or early damage assessment.

UrEDAS of Japan Railway group and SIGNAL of Tokyo Gas Company are the pioneers of such systems. Detecting the arrival of P-waves by its own network near the source, UrEDAS estimates the location and magnitude of an earthquake very quickly, then uses this information to stop high-speed trains before the arrival of S-waves. SIGNAL performs damage estimation of a natural gas network based on extensive earthquake monitoring and GIS, and uses this information for the decision-making whether or not to shut off medium-pressure gas supply. Natural gas supply systems also have other safety algorithms: automated shut-off valves at district regulators and microcomputer meter at customers.

For expressway networks in Japan, a number of instruments were increased after the 1995 Hyogoken-Nanbu (Kobe) Earthquake. The recorded peak ground motion values are used to control highway traffic: closing the entrance or reducing the speed limit depending on the severity of ground motion. The other lifeline systems also have their own seismometers. The electric power generation plants and substations have accelerometers and stop their operations if the ground motion exceeding a critical level is detected. Some water supply systems also have seismic sensors. The water storage tanks of gravity distribution type have automated shut-off valves to avoid running out of water from pipe breaks. The Kobe Water Department saved water in the tanks by its automated shut-off valves immediately after the Kobe earthquake. Elevators in buildings usually have seismic sensors. If the peak acceleration exceeds a certain level, elevators stop at the nearest floor automatically to avoid trouble.

Local governments and fire departments have recently installed early earthquake damage estimation systems using seismic information from national seismic networks and their own instruments. Tokyo Fire Department developed an early damage assessment system for fire fighting and rescue operations. If an earthquake occurs the system estimates the distribution of peak ground motion, the number of collapsed buildings, fire outbreaks and human casualties. A number of similar early damage assessment systems have been developed or are being developed by many local jurisdictions as well as national government agencies. These early warning systems and early damage assessment systems are expected to play a vital role to reduce secondary disasters due to earthquakes in Japan.