2007 AGU Fall Meeting in San Francisco

Integrated System for Earthquake Early Warning and Quick Response Against Strong Motion
- In Case of the Tokyo Metro Company

Tsutomu Sato, Jun Saita and Yutaka Nakamura
System and Data Research, Co., Ltd.

In July 2005, an earthquake of M6.0 attacked the Tokyo metropolitan area. This earthquake occurred at 35.5N and 140.2E with about 73km in depth, and the maximum JMA intensity was 5+ corresponding to MMI VIII approximately. This earthquake occurred at north-west of Chiba prefecture and caused a traffic disturbance widely in Tokyo metropolitan area. All the train operation had been stopped for a long time after the earthquake, although a severe damage was not caused even in the area of high intensity. The longest down time for the train operation was more than seven hours.

After the earthquake, we proposed a new system for early warning and quick response. Tokyo Metro Company accepted our proposal, and we replaced and built the new early warning/quick response system as followed.

The system consists of two seismometer networks. One is the early warning system FREQL network with six seismometers to control or stop the train operation immediately after the earthquake occurrence. And the other is the portable digital seismometer AcCo network distributing 33 seismometers in every about three kilometers mesh to grasp more detailed seismic motion on their service area.

The information from both FREQL network and AcCo network are gathered to the operation center and displayed on the individual monitoring system. The monitoring system for AcCo can indicate the integrated information from AcCo and FREQL on the subway network image. The AcCo monitoring system is also installed on the control table for each subway line.

At the time of the earthquake, the early warning system detects at first the earthquake immediately and then the 33 local seismometers inform the actual earthquake motion of each site independently and rapidly. This system realized quick response and restart of the train operation because the early warning became faster and checking zone after earthquake was optimized. This updated system is expected to realize quicker response during and after.

For the large system as the train operation, it is necessary for the control against the earthquake to equip the system not only to issue the early warning but also to support the quick and rational recovery work after the earthquake.

SESSION: S13 - Earthquake Early Warning: Design and Application Around the World


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