February 2023

DAS observation which measures the vibration applied to the fiber optic cable, was started in Kumamoto. The advantage of the DAS observation is the dense measurement points, so this observation aims to analyze small earthquakes that occur near the fault and to estimate shallow heterogeneous structures. We use the 40km long fiber optic cable along Route 3. The Ministry of Land, Infrastructure, Transport and Tourism, Kyushu Regional Development Bureau, Kumamoto Office of River and National Highway owns the cable. Assoc. Prof Emoto and M1 student Hamanaka installed the DAS equipment. Due to the heavy traffic, analyzing the earthquake is difficult. However, we try to retrieve important information from vast and precious data. That is a challenging but exciting part of the DAS measurement in the urban area. An example of the DAS record. We can see the wavefronts of P and S-waves of the earthquake near Fukuoka. This is the image of about 20,000 waveforms observed every 2m.

DAS Observation in Kumamoto