H/V spectral ratio characteristics of hidden fault site based on ambient noise test

Ambient noise research has become a hot spot in geological exploration, but the research on ambient noise in alpine and gorge regions of Southwest China is still in its infancy. Based on more than 60 ambient noise tests conducted in the hidden fault crossing area of Anshun field in Shimian county, Sichuan, this paper explores the influence of hidden faults on the H/V spectral ratio characteristics of ambient noise. The results show that after excluding predominant-frequency areas that may be caused by the influence of rivers, the H/V spectral ratio curves are characterized by high frequency, low H/V spectrum ratio, and multi peak frequency on the fault zone. In addition, we estimated the thickness of overburden in this field by analyzing the predominant frequency of this test, and the calculation results of the overburden layer show thickness difference of 5−10 m in some strong weathering areas and high frequency areas of rivers. Moreover some areas with large changes in overburden thickness obtained by ambient noise array inversion are consistent with the trace distribution of the hidden faults. This study attempts to reveal the traces of hidden faults by using the ambient noise method, which provides a new reference basis for the exposure of hidden faults.