Local earthquake response on the submarine communication cable in the northern South China Sea.

As a new seismological monitoring technology, distributed acoustic sensing (DAS) not only provides a high-precision seismic observation method, but also uses undersea communication fiber or dark fiber to reduce the layout cost, and supports long-term observation for several years, and the sensing resolution reaches the scale of meters. This technique provides a broad prospect for seismic observation in oceanic area which is difficult to be covered by traditional seismic observation instruments. In this paper, we analyzed the DAS waveforms of 10 local-earthquake events waveforms recorded by offshore submarine communication cable in the northern South China Sea, and discussed the response ability of DAS system based on shallow sea communication cable to near-earthquake. It is found that the signals are affected by surface gravitational waves and micro seismic noise (Scholte Wave) generated by solid-liquid coupling motion. Then, waveform stacking, discrete wavelet transform, and empirical mode decomposition are used to denoise the signal in shallow sea area for extracting earthquake waveform. Submarine optical cable is the most widely distributed submarine signal monitoring system in the world. Long-term and cheap deep-sea seismic wave observation based on such the large-scale global ocean observation network can provide important data for the development of seismology.