A Case Study on Fiber Optic Interferometric Seafloor Seismic and Tsunami Monitoring System in South China Sea

A seafloor seismic and tsunami monitoring system based on fiber optic interferometric technology was developed and installed in the nearby waters at the Chinese State Oceanic Administration's (SOA) Wuchang (Hainan Province, China) monitoring site. The developed tricomponent fiber optic interferometric seismometer has a sensitivity of 57 dB (re: 0 dB = 1 rad/g), within the operation frequency range of 0.005-50 Hz, and a minimum detectable acceleration of 43.4 ng/√(Hz); while the fiber optic interferometric water-level monitor has an accuracy of ±1 cm, a measurement range of 0-110 m. The system has been operating continuously since its installation in October of 2017, and has been collecting data ever since during this long-term field trial. To date, there were 55 earthquakes with M L 6.0+ in the Northeast Asia area, and 39 earthquakes were recorded by our system. As examples, the detailed measurement results of two M L 6.0+ earthquakes in Indonesia are given.