Earthquake Early Warning System for Korea Train eXpress (KTX)

High speed train service, named Korea Train eXpress (KTX) was started in Korea with a maximum speed of 305 km/h in 2016. As a countermeasure against earthquake, earthquake early warning system (EEWS) was constructed for KTX. It consists of 48 accelerometers installed every 13 km along the railroad. Quick Seismic Characteristic Data (QSCD) was introduced to quickly evaluate possible earthquake damage of the railroad, such as long-span bridges. The QSCD is designed to use Peak Ground Acceleration (PGA) calculated per second as basis measure for warning. The EEWS is preset to issue two types of warning according to the PGA level: Slow-Down for 45 Gal and Stop-Train for 60 Gal.

ML 5.8 earthquake struck the city of Gyeongju on 12 September 2016. Another earthquake (ML=5.4) damaged a nearby city of Pohang on 15 November 2017, which is about a year later after the Gyeongju earthquake. The Gyeongju earthquake is the largest earthquake ever recorded since instrumental seismic observation started in Korea. At the time of the Gyeongju earthquake, the EEWS was operated well and issued a warning signal 5 seconds after origin time based on the PGA (93.5 Gal) detected at the station 1.2km apart from the epicenter. In case of the Pohang earthquake, a PGA value of 46.6 Gal leading to Slow-Down warning was detected at the station 40.2 km apart from the epicenter. This case study shows that the KTX EEWS responds practically and instantly to the moderate sized earthquakes in Korea.