Epicenter localization using forward-transmission laser interferometry.

Widely distributed optical fibers, together with phase-sensitive laser interferometry, can expand seismic detection methods and have great potential for epicenter localization. In this paper, we propose an integral response method based on a forward transmission scheme. It uses spectrum analysis and parameter fitting to localize the epicenter. With the given shape of the fiber ring, the integral phase changes of light propagating in the forward and reverse directions can be used to determine the direction, depth, distance of the epicenter, and seismic wave speed. For the noisy case with SNR = 20 dB, the simulation results show ultrahigh precision when epicenter distance is 200 km: the error of the orientation angle is ∼0.003°±0.002°, the error of the P-wave speed is ∼0.9 ± 1.2 m/s, the error of the epicenter depth is ∼9.5 ± 400 m, and the error of the epicenter distance is ∼200 ± 760 m.