A STUDY ON CHARACTERISTICS OF SOURCE PARAMETERS IN THREE GORGES RESERVOIR AREA

Digital seismic data recorded by 26 temporary stations from March to November in 2009 in the Three Gorges reservoir area were used to study the characteristics of anelastic attenuation in this region using the Atkinson's method and to obtain the site responses of 26 temporary stations using the Moya's method.Moreover,source parameters of 1020 earthquakes with magnitude bigger than 0.1 were calculated and used to study the scaling relations among them.Our results show that(1)The anelastic attenuation in Three Gorges reservoir is Q(f)=112.0f 0.918,with a smaller value of Q0 and bigger value of η.Site responses of most temporary stations are 1～10 times except a few stations.(2)Seismic moment M0 increases with increasing magnitude ML and their statistical relationship is LogM0=1.07ML+9.76.Relationship between stress drop and magnitude is consistent with the result gained by Nuttli that intraplate earthquake follows the ISD model,with a statistical relationship LogΔσ=0.66ML-3.08.(3)Radiated seismic energy and apparent stress in Three Gorges reservoir all increase with increasing magnitude,indicating that a big earthquake is a more efficient radiator of seismic energy than a small earthquake.(4)Stress drops of reservoir induced earthquake are apparently smaller than that of tectonic earthquake with same magnitude,about 10 times smaller.These results may be due to the increase of pore pressure that leads to the occurrence of earthquake with a lower tectonic stress.