With a total of 38 seismic stations, Gaiacode has built a combined Earthquake Early Warning (EEW) and Structural Health Monitoring System (SHM) for the Turkish State Railway. This system will serve a dual purpose along the 174 kilometer long high speed rail line between the Turkish capital Ankara and the eastern Anatolian town of Yerköy. 15 of the seismic stations will be placed in regular intervals along the railroad tracks to continuously monitor the ground acceleration. If the measured “Peak Ground Acceleration” (PGA) tops a threshold value, the trains will be automatically slowed down or even stopped. Another set of 17 stations will be installed on a 1.4 kilometer long viaduct to record its structural integrity during earthquake shaking. A further 6 stations will perform a similar function in three railroad tunnels.
High Seismic Hazard
The area east of Ankara is a zone of high seismic hazard. At least five local earthquake faults lie close to the newly constructed high speed rail line. In addition, the east-west rail line itself runs at a distance of approximately 120 kilometers roughly parallel to the North Anatolian Fault, one of the most hazardous strike-slip faults in the world. During the last 80 years at least 12 major earthquakes with magnitudes of up to 7.8 occurred along this fault, resulting in more than 60,000 fatalities and causing massive damage.
Early Warning and Structural Health Monitoring
Each of the Early Warning stations consists of two three-component SIGMA feedback accelerometers which feed their analogue data into an eight channel TAU digitizer with a resolution of 24 bit per channel. The stations to monitor the structural health of the tunnels and the viaduct have a different layout. Each consists of two high resolution three component MEMS sensors and one one high resolution tilt sensor developed by Gaiacode. Their respective data are digitized in a nine channel TAU digitizer. In addition, the viaduct stations have sensors for wind speed and wind direction which are integrated with the MEMS and the tiltmeters. Along the viaduct, the 17 TAU digitizers will be connected serially to each other to reduce cable requirements.
In the early warning stations, the PGA values and values for the peak ground velocity as well as the peak ground displacement are calculated on-site. All digital data with a 100 samples/sec data rate will be transmitted in packets via optical fiber to the railway operations center in Ankara with the extremely low latency of 0.1 seconds. There they will be used in an automatic decision module to slow down trains if necessary. Also in the operations center the data stemming from the structural health monitoring stations are displayed in real time.
All elements of the equipment are manufactured and tested. The whole batch is ready to ship with an expected shipping date in the second half of 2022.