3:30 PM - 3:45 PM
[SCG53-01] Technical Progress of Earthquake Early Warning Methods for Shinkansen
★Invited Papers
Keywords:Railway, Earthquake Early Warning, initial P-wave, Estimation of seismic source parameters
The Shinkansen is an important infrastructure as a high-speed transportation system. However, the Shinkansen is constantly facing the risk of earthquakes, which can occur at anytime and anywhere around Japan. Because structural countermeasures such as seismic reinforcement have been implemented for the Shinkansen, the number of events in which Shinkansen structures are damaged due to earthquakes is currently limited. On the other hand, even in recent years, derailments of Shinkansen trains have been reported in the 2016 Kumamoto Earthquake and the 2023 off Fukushima prefecture earthquake. In order to prevent the trains from derailing due to seismic strong motion, it is important to suspend the trains emergently. Seismometers with earthquake early warning functions have been implemented for the Shinkansen and are in operation.
An earthquake warning system has been in place since 1965, after the Tokaido Shinkansen began operation, to suspend running trains. Initially, seismometers, called track-side seismometer, were installed in substations along the railway and a warning, called an S-wave alarm, was issued when a seismic motion exceeding a predefined threshold was detected. The substation shuts off the electricity and emergency brakes are applied to the running train to suspend. Next, when the Tohoku Shinkansen was extended in 1982, seismometer, called a front-detection seismometers, were installed along the coastline closer to the subduction zone, and a system was constructed to quickly detect seismic motions and suspend trains running away from tracks. The Urgent Earthquake Detection and Alarm System, called UrEDAS, which estimates the epicentral location and seismic magnitude using the initial P-wave motion and issues a warning, called P-wave warning, was developed and in operate on the Tokaido Shinkansen in 1992. Subsequently, the algorithm to estimate seismic source parameters was improved, and seismometers implementing an algorithm, called the B-Δ method, has been in operation since 2004. Thereafter seismometers implementing a further improved algorithm, called the C-Δ method, have been in operation since 2018 and continues to be in operation.
Seismometers installed on the Shinkansen have inherent problems to consider. First, it is to accurately discriminate between seismic motions and train-induced vibrations, because the seismometers are located right beside the tracks and are exposed to the vibration induced by running Shinkansen trains. Second, since the seismometers are installed in a substation, seismometers are environmentally susceptible to electromagnetic noise. The seismometers installed on the Shinkansen have been designed to counter these problems.
The earthquake early warning for the Shinkansen emphasize immediacy in order to apply braking to high-speed vehicles as quickly as possible, and thus applies estimated information which contains a certain amount of estimation error. In order to increase redundancy though multiplexing, information of Earthquake Early Warning from the Japan Meteorological Agency and data of ocean bottom seismometers from the National Research Institute for Earth Science and Disaster Resilience are utilized to issue warnings.
The earthquake early warning system for the Shinkansen have proven to work properly in the event of past earthquakes. For example, at the occurrence of the 2011 off the Pacific coast of Tohoku Earthquake, a front-detection seismometer where was closer to the hypocenter and away from the tracks issued a warning and the Shinkansen initiated braking about 15 seconds before a seismic strong motion reached the railway.
The effectiveness of earthquake early warning system for the Shinkansen has been shown in the past, and we will continue to improve the estimation accuracy of seismic source parameters and the reliability of seismometers operation.
An earthquake warning system has been in place since 1965, after the Tokaido Shinkansen began operation, to suspend running trains. Initially, seismometers, called track-side seismometer, were installed in substations along the railway and a warning, called an S-wave alarm, was issued when a seismic motion exceeding a predefined threshold was detected. The substation shuts off the electricity and emergency brakes are applied to the running train to suspend. Next, when the Tohoku Shinkansen was extended in 1982, seismometer, called a front-detection seismometers, were installed along the coastline closer to the subduction zone, and a system was constructed to quickly detect seismic motions and suspend trains running away from tracks. The Urgent Earthquake Detection and Alarm System, called UrEDAS, which estimates the epicentral location and seismic magnitude using the initial P-wave motion and issues a warning, called P-wave warning, was developed and in operate on the Tokaido Shinkansen in 1992. Subsequently, the algorithm to estimate seismic source parameters was improved, and seismometers implementing an algorithm, called the B-Δ method, has been in operation since 2004. Thereafter seismometers implementing a further improved algorithm, called the C-Δ method, have been in operation since 2018 and continues to be in operation.
Seismometers installed on the Shinkansen have inherent problems to consider. First, it is to accurately discriminate between seismic motions and train-induced vibrations, because the seismometers are located right beside the tracks and are exposed to the vibration induced by running Shinkansen trains. Second, since the seismometers are installed in a substation, seismometers are environmentally susceptible to electromagnetic noise. The seismometers installed on the Shinkansen have been designed to counter these problems.
The earthquake early warning for the Shinkansen emphasize immediacy in order to apply braking to high-speed vehicles as quickly as possible, and thus applies estimated information which contains a certain amount of estimation error. In order to increase redundancy though multiplexing, information of Earthquake Early Warning from the Japan Meteorological Agency and data of ocean bottom seismometers from the National Research Institute for Earth Science and Disaster Resilience are utilized to issue warnings.
The earthquake early warning system for the Shinkansen have proven to work properly in the event of past earthquakes. For example, at the occurrence of the 2011 off the Pacific coast of Tohoku Earthquake, a front-detection seismometer where was closer to the hypocenter and away from the tracks issued a warning and the Shinkansen initiated braking about 15 seconds before a seismic strong motion reached the railway.
The effectiveness of earthquake early warning system for the Shinkansen has been shown in the past, and we will continue to improve the estimation accuracy of seismic source parameters and the reliability of seismometers operation.