Calculation and Analysis of Environment Ground Noise Based on the PPSD Method for Yangjiang Guangdong Small Aperture Borehole Seismic Array

Based on the Probabilistic Power Spectral Densities(PPSD) method, the environment ground noise of ten sub-stations of Yangjiang Guangdong small aperture seismic array is calculated, the total archived continuous three-component seed data of five years from 2014 to 2018 are used. The monthly and annual continuity rates of those data is calculated. The results of environment ground noise were obtained by PPSD calculation for every hour, every day, every month, every year and five years. The results are summarized to analyze the stability and anomaly of environment ground noise. The results show that the environment ground noise level of each sub-station is stable in the past five years, which indicates that the change of underground platform foundation and the status of instrument operation are stable. The underground observation can avoid the human interference of production and activity on the ground, and solve the problem that the long-term construction and development of cities which destroy the environment of earthquake monitoring. But there also have some problems such as the sub-stations close to the sea are susceptible to the typhoon interference, the poor data continuity rate of sub-stations in wireless bridge communication mode, vertical component of instrument is relatively easily to abnormal situation, long maintenance period of underground equipment broken, etc.