11:30 AM - 11:45 AM
[SSS07-04] Analysis of directional characteristics of microseismic ambient noise in mainland China
Keywords:ambient noise sources, dominant azimuth, mainland China
The isotropy of ambient noise sources is fundamental to obtain accurate Green’s functions. However, due to the seasonal variability of oceanic activities, the orientation of microseismic noise sources shifts, and their energy fluctuates significantly. Mainland China, with its vast territory and extensive network of seismic stations established for earthquake monitoring, provides an ideal natural laboratory for studying the directional characteristics of microseismic noise. This study, based on the asymmetric characteristics of empirical Green’s functions, utilizes the dataset of 377,770 empirical Green’s functions for mainland China, published by Xiao et al. (2022, 2024). The primary focus is on examining the directional characteristics of microseismic noise sources in mainland China and conducting a preliminary analysis of their excitation mechanisms. The findings reveal a significant spatial distribution inhomogeneity of microseismic noise sources across mainland China: The azimuthal anisotropy and dominant azimuth of secondary microseisms (8–10 s) show the highest SNR along coastal areas, whereas primary microseisms (10–20 s) exhibit the opposite trend. These directional distribution characteristics reflect the excitation mechanisms of ambient noise sources: (1) In coastal regions, the interaction between incident and reflected ocean waves nearshore excites secondary microseisms (8–10 s). The dominant azimuths within this period range primarily point towards the Indian Ocean and South Pacific, followed by the South Atlantic. (2) Combining global ocean significant wave height statistics, primary microseisms (10–20 s) are excited by deep-sea ocean waves acting on the seafloor in remote oceanic regions, with the main sources originating from the North Atlantic, followed by the Indian Ocean and North Pacific.