Characteristics of source parameters of the Shanxi Reservoir earthquakes in Zhejiang region

According to the seismic data of 1 360 earthquakes with M_L0.5-4.4 occurred in Shanxi Reservoir from January of 2014 to December of 2015, which were recorded by the Regional Digital Seismic Network of Zhejiang Province, this paper obtains the source displacement spectra by using Fourier integration of velocity spectrum in the frequency field based on the Brune's model, after the geometrical diffusion correction, medium attenuation correction and instrument correction of the velocity records from the stations, and then the corner frequency and the source displacement spectra at the zero frequency are acquired with the genetic algorithm. And then the radius of the epicenter, the seismic moments and other small local earthquake source parameters are calculated. Furthermore, this paper systematically analyzes the characteristics of the source parameters and the relationship among the parameters. The results show that: seismic moment ranges 10¹⁰-10¹⁴ N·m, the range of source radius is 33-550 m, the corner frequency ranges 2.4-39.7 Hz, seismic stress drop is in the range of 0.04-6.74 MPa, and apparent stress is in the range of 0-2.75 MPa. The result also show that there is some log-linear or semi-logarithmic linear relationships among the seismic moment, corner frequency, Richter magnitude, moment magnitude and other source parameters. In the space domain, the stress drop and the corner frequency are higher at northwest section of Shanxi Reservoir area and lower at southeast section. In addition, there is opposite relationship between the stress drop and the seismic moment in space, meanwhile the corner frequency is negatively correlated to the source radius in space.