利用深度震相确定芦山地震主震及若干强余震的震源深度*

(四川省地震局,四川 成都 610041)

芦山地震; 深度震相; 动校正叠加; RDPM; 震源深度

Determining Focal Depth of Lushan Main Shock and Several Strong Aftershocks by Using Depth Phases
LONG Feng,RUAN Xiang,GONG Yue,ZHAO Min,WU Peng

(Earthquake Administration of Sichuan Province,Chengdu 610041,Sichuan,China)

Lushan earthquake; depth phase; dynamic-correction stacking; RDPM; focal depth

备注

通过收集芦山地震主震的远震波形记录,利用pP深度震相的动校正叠加法对主震的震源深度进行了确定,不同窗长的计算结果显示该地震震源深度在(16±1)km处,与目前主流结果(14~18 km)一致; 同时,利用“区域深度震相建模”(Regional Depth Phase Modeling,RDPM)方法对4次MS4.0以上强余震进行了震源深度的确定。通过对波形的比对,选择LTA台和PmP-sPmP震相对。为确保结果的可靠性,使用远震接收函数的H-k叠加结果修改了初始速度模型的莫霍面深度及波速比,并使用CAP方法计算了这些事件的震源机制解。结果 显示,由RDPM得到的震源深度与利用区域直达波震相获得的精确定位结果几乎一致; 4个事件中有3个的深度范围与CAP的结果相近,有2个与台网快报相差无几。事实证明,利用远震深度震相和区域深度震相都能对震源深度有很好的约束,对于台站稀疏的地区来说,深度震相提供了一种相对准确的震源深度确认途径。

Firstly,the teleseismic waveforms of the Lushan main shock were colleted,and the focal depth was determined by using the dynamic-correction stacking method of the pP depth phase,the calculation results of different window size show that the focal depth of the main shock is(16±1)km and is consistent with the current mainstream results(14~18)km. In addition,the focal depths of four MS≥4.0 strong aftershocks were determined by the “Regional Depth Phase Modeling”(RDPM). Through the waveform comparison,the LTA Station and the phase pair of PmP-sPmP were chose. To ensure the reliability of the results,we revised the depth of Moho and the Vp/Vs in the initial velocity model by using the H-k stacking from teleseismic receiver funtions of LTA station and the focal mechanism solutions by CAP method. The results show that the focal depths which is calculated by the RDPM and the precision location obtained by the regional direct phase are almost identical. The focal depth range of three events from four events is similar with that of the CAP method,and the focal depth range of two events is almost the same with the results of network express. The facts prove that teleseismic or regional depth phase both have the good constrain on the focal depth. For the region of sparse stations,the depth phases provide a relatively accurate way to confirm the focal depth.