【摘要】 2013年吉林前郭M_s5.8震群为爆发性震群,目前余震活动仍然在持续.基于吉林、辽宁、黑龙江、内蒙古四省地震台网记录的前郭震群波形资料,利用波形信噪比、震源类型、台站及速度模型组合的指标选择最佳的反演方案,应用矩张量的三种反演模式,对序列中5个M_s≥5.0地震进行矩张量反演研究,获得了全矩张量、偏矩张量和纯双力偶的矩张量.使用F-test对地震的三种模式的矩张量反演结果进行显著性检验来确定最佳反演模式.结果显示,5个地震的最优矩张量解均为全矩张量模式反演获得的结果,其双力偶分量仅有20%~65%,矩心深度位于地下3~4 km处,地震在Hudson震源类型图上的投影远离双力偶震源类型区域.这些结果表明,震源类型并非典型的构造地震,推断前郭地震可能是与人类活动有关的诱发地震.更多还原

【Abstract】 The Qianguo M_s5. 8 seismic swarm was a strong sudden event in Jilin in 2013. Since then its aftershock activity still continues,but its mechanism is a hotly debated issue. The seismic moment tensor solution is an efficient way to understand such a seismic swarm. In the present study we invert for the full moment tensor solutions of the five events with M_S≥5. 0 using the high-signal-to-noise-ratio seismic waveform data collected from the Jilin, Liaoning, Heilongjiang,and Inner Mongolia provincial Digital Seismic Networks. The double couple component and centroid depth are two useful parameters in determining which type of event the Qianguo seismic swarm is. The present study used the ISOLA method to obtain the full moment solutions and divided them into three parts: ISO( Volumetric), CLVD(Compensated linear vector dipole),and DC(Double couple). According to the number of seismic stations and their azimuth gap among the stations used, the five parameters, such as VR, CN, SNR, FMVAR, and ST VAR, are used to choose the optimal inversion scheme. During the inversion, we take into account the effects of seismic stations and various velocity models on the results. The results show that the double couple components of the five events from the full moment tensor solutions are all located in the range of 20%~65%,and the centroid depths are 3~4 km. The five events on the Hudson source plot are all apart from the double couple source region, which suggests that the source types are not typical tectonic earthquakes. Using the F-test, we ascertain that the full moment tensor solutions of the five events are reliable,and have the highest statistical significance. Such a low DC component and shallow centroid depths imply that the Qianguo seismic swarm is not typical tectonic earthquakes but a possible seismic event related to human activities.更多还原