2013年岷漳地震和2014年景谷地震的能矩比对比研究

Comparative study on the energy-moment ratio between the 2013 Minzhang earthquake and the 2014 Jinggu earthquake

2013年岷漳地震和2014年景谷地震两个地震的矩震级均为M W6.1,但相同等级烈度区域的面积差异显著,前者均明显大于后者.地面震动的强烈程度与震源破裂过程中辐射的地震波高频成分密切相关,作者系统地测定与研究了这两个地震的震源谱和反映其震源特征的能矩比等震源参量.结果表明,虽然岷漳地震和景谷地震释放的地震矩基本相同,分别为1.6×10^18 Nm和1.8×10^18 Nm,而且前者还比后者略小些,但其释放的地震波辐射能却差异显著,分别为1.3×10^14 J和0.6×10^14 J;因而前者的能矩比(8.1×10^-5)是后者能矩比(3.3×10^-5)的大约2.5倍.相应地,岷漳地震的视应力和应力降也都明显大于景谷地震的视应力和应力降.此外,这两个地震震源谱结果均显示出其高频趋势均按角频率ω的-2幂次衰减,符合“ω2模式”;采用理论震源谱公式计算结果分别约占实际结果的54%和50%,两个地震的地震波辐射能解析解之间的差异依然约2.3倍.震源破裂特征的显著差异导致岷漳地震单位地震矩释放的地震波辐射能更多,即岷漳地震能矩比更大,是导致这两个矩震级均为M W6.1地震的地震烈度差异显著的一个重要原因.

The moment magnitude of the Minzhang earthquake in 2013 and the Jinggu earthquake in 2014 are both M W6.1,but the former caused significantly larger area of the same isoseismals than the latter.The isoseismals of ground shaking is closely related to the high-frequency components of the seismic waves radiated during the source rupture.The source spectra of these two earthquakes and the energy-moment ratio which reflect the source characteristics,are measured and analyzed systematically.The results show that the seismic moment released by the Minzhang earthquake and Jinggu earthquake have little difference,1.6×10^18 Nm and 1.8×10^18 Nm,respectively.The seismic moment of the Minzhang earthquake is slightly smaller than the seismic moment of the Jinggu earthquake,but the radiated energy of the Minzhang earthquake and Jinggu earthquake are 1.3×10^14 J and 0.6×10^14 J,respectively.Therefore the energy-moment ratio of the Minzhang earthquake(8.1×10^-5)is about 2.5 times that of the Jinggu earthquake(3.3×10^-5).Accordingly,the apparent stress and the stress drop of the Minzhang earthquake were significantly greater than that of the Jinggu earthquake.In addition,the modeling results of two earthquakes show that the high-frequency attenuation of source spectra are both consistent withω2 model.The radiated energy results calculated by the theoretical formula alone account for about 54%and 50%of the actual results respectively,and the difference of the theoretical radiated energy results between two earthquakes is still about 2.3 times.The significant difference of source rupture characteristics lead to different energy radiated per unit seismic moment.Minzhang earthquake has larger energy-moment ratio than the Jinggu earthquake,which is one of the important reasons resulting that the Minzhang earthquake is of larger isoseismal area than that of the Jinggu earthquake with the same isoseismal.