Optimising the seismic early warning system for the Tohoku Shinkansen

Achilleas Papadimitriou1, Daniele Veneziano2
1Civil Engineering Department, National Technical University of Athens, 42 Patission Str., 10682 Athens, Greece.
Tel. : +30-1-772 37 45, Fax: +30-1-772 34 28,
E-mail: loupapas@alum.mit.edu
2Civil and Environmental Engineering Department, Massachusetts Institute of Technology, 77 Massachusetts Ave., Rm. 1-348, Cambridge MA 02139, USA.
Tel. : +1-617-253 71 99 Fax: +1-617-253 60 44,
E-mail: venezian@mit.edu

The Tohoku Shinkansen is a high-speed passenger train that connects Tokyo to the northern city of Morioka in Honshu, Japan. The line is protected by a seismic early warning system, which includes two sets of accelerometers: one set is deployed along the line (wayside system), while the other comprises eight accelerometers placed along the eastern coast of Honshu (coastal system). The coastal system is designed to protect the train against earthquakes with origin in the highly active offshore subduction zone. It causes trains to automatically stop when the ground acceleration exceeds a preset limit. At the time of the study, the system was causing frequent train delays, while providing an unclear level of seismic protection. We have found that, with the current early warning system, the rate of earthquake-induced derailments along the entire 500 km line is about 2-3 per 100 years. By changing various system parameters, one can lower this rate to about 1 derailment every 100 years while reducing the rate of false alarms and unnecessary delays by a factor of about 40. These benefits arise mainly by operating the wayside system on spectral acceleration rather than peak ground acceleration. The level of risk varies along the line and is sensitive to the attenuation and fragility models used in this analysis.