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  1. TRANSPORTATION
  1. ANTI-EARTHQUAKE MEASURES FOR THE SHINKANSEN (BULLET TRAIN)

The Sanyo-Shinkansen (bullet train between Osaka and Kyushu) was severely damaged by the Great Hanshin Earthquake with eight places of elevated railroads and bridges collapsed, and had to stop its operation between Shin-Osaka and Himeji for 81 days. It was small mercies that the earthquake occurred at 5.46, in the early morning, right before the first train was to start running. If the disaster had happened later of the day, it would have been a catastrophe with the running trains derailed or overturned.

Anti-Earthquake Measures for Shinkansen

Earthquake is a very dangerous factor to the Shinkansen which runs at a high speed, and various quake-resistance systems have been introduced. One is a system to immediately stop and protect the train when an earthquake happens. This system has two detection systems -- (1) a detection system utilizing seismographs set in every substation along the Shinkansen line, and (2) a detection system utilizing seismographs set along the coastline at regular intervals. However, only the latter system had been installed into the Sanyo Shinkansen before the Hanshin Earthquake occurred, though the Tohoku and Tokaido Shinkansen lines had been covered by both of them. The Japanese National Railways Corporation (the predecessor of the present JR) and West Japan Railway Company had underestimated the risk of earthquake in the Sanyo Shinkansen area, and regarded the setting up the system using the coastline seismographs as quite enough for the Shinkansen route with many tunnels.

Improvement of Seismic Capacity

The West Japan Railway Company, directly hit by the Great Hanshin Earthquake, reinforced earthquake-resistance and also took two more new measures. One is that they newly established the second control station in Shin-Osaka in February, 1999, besides the existing one in Tokyo, to diversify risk to the traffic control system of the Tokaido and Sanyo Shinkansen lines, and another one is that they installed a system called "UrEDAS (Urgent Earthquake Detection and Alarm System)" in November, 1996. UrEDAS is a system to detect the preliminary tremor of an earthquake (P wave) and stop or reduce the speed of trains before the principal shock (S wave) arrives. As a result, the seismic capacity of the Sanyo Shinkansen was greatly improved.

Weakness of the UrEDAS System

There remains, however, some serious problems as follows. The first one is that the peak speed at which the Shinkansen currently runs is 270-300 kph as a result of speed competition. The time delay of the UrEDAS is said to be 26 seconds on average, which means that even if the system works, a train running at 240-270 kph will most likely keep running for about 1.5km on the violently shaking construction before managing an emergency halt (NAKAMURA Yutaka, March, 1996). The train may get derailed or overturned, or crash into a collapsed building. The second one is that UrEDAS is a system which works more effectively when the seismic source is further away. It is incompetent when an earthquake occurs directly underneath the area where the train is running at high speed. The system is almost defenseless against such an inland, local earthquake like the Great Hanshin Earthquake.

Japan Railways and related organizations should work out a countermeasure against an inland, local earthquake as soon as possible. The present anti-earthquake measures are not sufficient, while a great earthquake is expected to surely come. To make the potential damage as little as possible, they should stop further increasing the Shinkansen's speed.

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(ABE Seiji)