The influence of Typhoon Hagupit and Typhoon Bavi on microseisms

Typhoon-induced waves can usually enhance the microseisms energy, the generation mechanism and source locations of microseisms are controversial. We calculated the power spectral density and carried out polarization analysis of the continuous waveform data of seven wide-band seismic stations on the coast or inland from July 1 to September 1, 2020. The variation of power spectral density in different frequency bands during typhoons has been quantitatively discussed, and the distribution of noise sources at the seismic stations SSE, DYS, HUH, TPS and QHS were studied. The results show that the power spectral density of double-frequency microseisms significantly increased after Typhoon Hagupit and Typhoon Bavi, especially the long period double-frequency microseisms. The single frequency microseisms and microseisms with period ≥20 s increased inconspicuously. The short period double-frequency microseisms recorded at SSE, DYS, HUH, TPS, and QHS seismic stations are affected by different sources in the adjacent sea area. The sources of the long period double-frequency microseisms are consistent, pointing to the south-south-west direction, which may be affected by the source area of the South China Sea or further south. The single frequency microseisms are affected by different noise sources along the coastline.