新冠肺炎疫情对佘山与大洋山地震台背景噪声的影响

人类的生产生活产生的振动会以高频地震波的形式被地震台站所记录。2020年1月，新冠肺炎疫情爆发，为了应对此次疫情，各地政府分别启动应急响应，国内地震记录出现最长、最突出的人为地震降噪期。各地震台站背景噪声显著下降，在人口稠密及工业发达地区尤为明显。同时，静噪期为探测地下地震源的微弱信号提供了可能。静噪期内，佘山地震台2 Hz频点背景噪声功率谱密度值比平时降低10 dB，而大洋山地震台10 Hz频点背景噪声功率谱密度值较平时降低约5 dB；佘山地震台2—10 Hz以及大洋山地震台10 Hz以上频率的背景噪声受静噪期影响明显。结合地震台站所处位置分析，疫情期间佘山地震台附近人口流出较多，2—10 Hz频率的背景噪声变化明显；大洋山地震台背景噪声则受工厂、轮渡、高速汽车等影响较大，f ≥10 Hz的背景噪声变化显著，而频率在2—10 Hz则无明显变化，表明该台人口总数趋于平稳。地震噪声和人类活动之间的相关性表明，地震学研究可以提供实时人口动态估计。

Analysis of seismic ambient noise of Sheshan and Dayangshan seismic stations during the COVID-19 epidemic

The vibrations generated by human activity are recorded by seismic stations as high-frequency seismic records. In January 2020, the COVID-19 broke out. In order to deal with the COVID-19 epidemic, local governments launched emergency responses, leading to the longest and most prominent artificial seismic noise quiet period on record in China. The background seismic noise energy of each station decreased significantly, especially in densely populated areas and industrially developed areas. The background seismic noise quiet time also makes it possible to detect weak signals from underground earthquake sources. During the background seismic noise quiet time, the 2 Hz ambient noise energy of the SSE station was reduced by 10 dB compared with usual, while the 10 Hz ambient noise energy of the DYS station was reduced by about 5 dB. The impact is obvious. The analysis combined with the location of the station shows that, during the COVID-19 epidemic, there was a large people outflow near the SSE station, and the background seismic noise at 2-10 Hz changed significantly; while the background seismic noise at the DYS station was greatly affected by factories, ferries, high-speed cars, etc., resulting in significant background seismic noise changes in ≥10 Hz frequencies and no obvious changes in the frequency band of 2-10 Hz, indicating that the total population near the DYS station tends to be stable. The correlation between seismic noise and human activity suggests that seismology can provide a real-time estimate of population dynamics.