[S-TT35] Seismic monitoring and processing system

[STT35-P02] High-density seismic observation using optical fiber laying along a Shinkansen with a Distributed Acoustic Sensing (DAS) technology

*Masayuki Yoshimi¹, Satoshi Ide², Shuji Iwata³ (1.Geological Survey of Japan, AIST, 2.Department of Earth and Planetary Science, Tokyo Univ., 3.Central Japan Railway Company)

Keywords:DAS, Seismic observation, Train induced vibration

High-density seismic observation using a DAS (AP sensing N5226A) instrument was carried out using a communication optical cable installed along the Shinkansen track. The measurement target was a 5.8 km section in western Shizuoka Prefecture (4 km of which was along the Shinkansen service line, and the rest was the line to the factory and the factory site). Four optical cable cores were connected at the cable junction to form a 25-km-long single optical path. Seismometers (Mitutoyo JEP-6A3 + LS8800 data logger) were installed at two locations along the optical fiber for comparison use. The observation period is from 21:00 on 2021/01/12 to 12:00 on 2021/01/20. Data were acquired almost continuously while changing the observation parameters (sampling frequency [500, 1000, 2000 Hz], spatial sampling [1.27, 2.55, 5.1 m], and gauge length [5.1, 10.2, 20.4, 40.8 m]). The maximum amount of data was about 3 TB per day.
The optical cables in the measurement section were laid on various types of ground and structures such as viaducts, embankments, girder bridges, and ground surface. The difference in vibration characteristics caused by the installation environment of the optical cable is clearly recognized in the record. We are going to analyze the vibration characteristics of each type of structure and to study the applicability of the system to natural earthquake observation.