2017年9月23日朝鲜ML3.4地震矩张量反演

利用区域地震台网数字波形资料，对2017年9月23日朝鲜M_L3.4地震进行地震矩张量反演计算与参数稳定性评估，获得了此次地震的震源机制解.结果表明，地震矩心深度为3 km，标量地震矩为1.34×10¹⁴ N·m，矩震级为M_W3.4.地震矩张量结果分解后，双力偶分量（DC）为96.4%，补偿线性矢量偶极分量（CLVD）为-0.8%，震源体体积变化的各向同性分量（ISO）为-2.8%.主压应力P轴方位角为144°，倾角为74°，主张应力T轴方位角为341°，倾角为15°.其中一个节面的参数为：走向248°，倾向60°，滑动角-94°.地震震源体积变化分量很小，震源机制类型属于典型的由断层剪切位错引起的正断层型地震事件，且主张应力T轴方向与区域近地表应变率场方向一致.由于朝鲜2017年9月3日核试验释放的能量对局部区域应力场进行了扰动，致使核试验场附近地壳岩体处于破裂的临界状态，2017年9月23日朝鲜M_L3.4地震事件可能是区域应力场作用下的一次山体滑动事件.

The moment tensor of ML3.4 earthquake on September 23,2017, Democratic People's Republic of Korea (DPRK)

According to the China Earthquake Networks Center(CENC),an earthquake event occurred at Huataishan near the nuclear test site in Hamgyong of Democratic People's Republic of Korea (DPRK),with a focal depth of 0 km and a local magnitude of 3.4.It is important to determine the focal mechanism for further identifying it from underground nuclear test,natural earthquake,landslide and collapse.Based on the digital seismic data recorded on a regional network installed in Northeastern China,we investigated the focal mechanism for this event.The seismic moment tensor was determined with uncertainty estimation.The results show that the centroid depth is 3 km,the scalar seismic moment is 1.34×10¹⁴ N·m,and the moment magnitude is M_W3.4. The moment tensor solution was decomposed to DC (Double couple),CLVD(Compensated linear vector dipole) and ISO(Volumetric) components,and their values are 96.4%,-0.8% and -2.8%,respectively,where the volume component of seismic source body seems to be very small and was neglected in the solution.The azimuth and plunge of the principal compressive stress P axis are 144° and 74°,respectively.The azimuth and plunge of the principal tensile stress T axis are 341° and 15°,respectively.The strike, dip and rake are 248°,60° and -94°,respectively.The focal mechanism can be characterized by double couple model as a normal faulting mechanism.The direction of the main tensile stress is in agreement with one of regional strain rate field near surface.The huge energy from the nuclear test on September 3,2017 have disturbed the local crustal stress field.We suggested that the regional stress field triggered a natural event which may contribute to the M_L3.4 earthquake.