Temporal and Spatial Images of Ambient Noise Intensity in the Chinese Mainland

Successive waveforms of the vertical component recorded by 888 broadband seismic stations in the China Seismography Network from January, 2010 to June, 2011 are used to investigate the temporal and spatial distribution of ambient noise intensity, and the images of ambient noise intensity at the period of 10s in the Chinese Mainland are obtained. The temporal variation of ambient noise intensity shows some seasonal and periodic characteristics. The maximum ambient noise intensity occurred from January, 2011 to March, 2011. The spatial distribution images of ambient noise intensity show obvious zoning features, which doesn''t correlate with surface geology, suggesting that the noise field is stronger than the site factors. The strength in southeastern coastal areas reaches its maximum and generally decreases toward to inland areas, and arrives at the minimum in the Qinghai-Tibetan Plateau. The zonal intensity distribution is probably correlated with ocean tides from the Philippine Ocean and the Pacific Ocean. It also shows that the influence from the Indian Ocean seems small. However, the ambient noise intensity increases to a certain degree in the Xinjiang area, indicating that the main source of ambient noise in the western area of the Chinese Mainland is not derived from the East and South China Sea, but rather from the deep interior of the Eurasian continent. The ambient noise intensity obtained in this study can supply reference for seismology research based on ambient noise correlation. Moreover, it can supply basic data for attenuation research based on ambient noise, and thus help achieve the object of retrieving the attenuation of Rayleigh waves from ambient noise.