Research on The Source Parameters and Scaling Relations of Earthquakes in Weihe Basin and Its Adjacent Area

Abstract

By using the data recorded in Shaanxi seismic network, seismic source parameters were determined through spectrum analyzing basing on Brune’s source model for 125 small to moderate earthquakes (1.1 ≤ ML ≤ 4.8) from 1997 to 2016 in Weihe basin and its adjacent area. Seismic radiated energies were also obtained through integral of observed velocity spectra. The relations between stress drop, scaled energy E s / M 0 and Zúñiga parameter ε with seismic moment are analyzed. The results show that the earthquakes are with low stress drop in this area, the mean value is 0.16 MPa. More than 90% of the events in the region observed the ε value is less than 1. The low stress drop and low ε value indicate that earthquakes in this area can be explained by fractional stress drop mechanism or low effective stress model. These may be the result of mature fault activity, however, it cannot be ruled out effect of underground fluid. The scaled energy of earthquakes (1.3 ≤ MW ≤ 3.6) in this area is less than that of larger earthquakes (3.6 ≤ MW ≤ 6.0) in other areas. The earthquakes in this area are fairly small, so the heat energy generated in the rupture process is small, which is not enough to produce melting along the fault plane. With large dynamic friction force, it is not easy to produce rapid brittle rupture, resulting in low scalsed energy.