[S-TT38] Seismic monitoring and processing system

[STT38-P03] Super-dense seismic observation using optical fiber sensing along Route 9 in Kyoto

*Masatoshi Miyazawa¹, Kentaro Emoto², Hisashi Nakahara², Takeshi Tsuji³ (1.Disaster Prevention Research Institute, Kyoto University, 2.Graduate School of Science, Tohokuk University, 3.Department of Earth Resources Engineering, Kyushu University)

Keywords:DAS, onshore seismic observation, seismic wave field, M5.1 Noto earthquake, M5.3 and M4.9 Hida earthquakes

Distributed acoustic sensing (DAS) is a new technique to measure spatio-temporal strain changes along an optical fiber cable utilizing Rayleigh scattering. The advantages of its application to seismic observations include that a pre-existing optical fiber cable can be used as a sensor, providing a high-density seismic array, and the data can be acquired at a high sampling rate. Using the DAS system, we measured the strain rates using a 50 km-long optical fiber cable along Route 9 from Kyoto station to Kyotamba town that extends in an NW-SE direction, during the period from Aug 23 to Sept 24, 2021. The spatial sampling was 5.1 m, corresponding to the total number of channels of 9,788, and the temporal sampling was 500 sps. We observed local earthquakes with magnitudes from 0.4 to 3.2 and some moderate earthquakes that occurred several hundreds of km far from the cable, e.g., the M5.1 Noto earthquake (Sept 16) and the M5.3 and M4.9 Hida earthquakes (Sept 19).