Study on the Characteristics of Seismic Source Parameters in Chongqing Region
Based on the waveform data of 256 earthquakes with magnitudes ranging from ML2.5 to 5.5,recorded by the Chongqing Digital Seismic Network from 2010 to 2021,we conducted corrections for medium attenuation,site response,instrument response,and geometrical spreading in the frequency domain for the station records.This yielded velocity spectra,from which source displacement spectra were derived using the Brune model.The zero-frequency limit(Ω0)and the corner frequency(fC)were extracted using a genetic algorithm,which then allowed us to calculate scalar seismic moment(M0),the source rupture radius(r)and the stress drop(Δσ).Least squares fitting was used to calibrate the relationships between these parameters.The results show that the moment magnitude Mw ranges from 2.5 to 4.6,the fC ranges from 1.2 to 4.9 Hz,the M0 ranges from 6.52×1012 to 9.19×1015 N·m,the r ranges from 272 to 1,107 m,and the Δσ ranges from 0.02 to 10.90 MPa.The the apparent stress(σapp)ranges from 0.007 to 4.42 MPa.There are certain linear,semi-logarithmic,or double-logarithmic relationships between the source parameters.Notably,the double-logarithmic relationship between Δσ and M0(lgΔσ=0.647 3lgM0-3.693 6)conforms to Nuttli's ISD model.Spatial distributions show that fC is lower in the central part of the study area and higher in the eastern and western parts,with a negative correlation between fC and r.Stress drop Δσ is higher in the north and lower in the south,and there is a positive correlation between M0 and Δσ in space.
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