基于程函方程的初至P和sPg波走时联合地震定位方法

An eikonal equation-based earthquake location method with joint inversion of the first P and sPg traveltimes

由于初至波到时对震源深度敏感程度低,导致初至波到时定位难以获得可靠的震源深度信息.为了提升震源深度的定位精度,前人提出深度震相走时约束.深度震相定位方法利用深度震相对震源深度敏感的性质测定震源深度,极大的提高了震源深度的精确度.深度震相定位方法中,理论走时常在层状模型中计算获得,当实际地下结构与层状模型之间存在较大差异时,由深度震相方法测定的震源深度将会偏离真实深度.为了提高震源深度的测定精度以及减小速度模型误差对地震定位的影响,本文使用快速行进法求解程函方程获得非均匀模型中的初至P和sPg震相走时,并联合这两种走时开展重定位研究.以2022年四川泸定MS6.8地震为例的合成数据测试和实际定位结果显示,本文基于程函方程的初至P和sPg波走时联合地震定位方法能显著提高地震定位的精度.

The first arrival times are widely used in earthquake location.However,the earthquake location methods using the first arrival times lack constraints on the focal depths due to the traveltimes of the first P-phase are less sensitive to focal depth.To improve the accuracy of focal depth,regional depth-phase methods have been proposed.The regional depth-phase methods greatly improve the precision of focal depth because the regional depth-phases are sensitive to the focal depth.Owing to the theoretical arrival time differences are calculated in one-dimensional layered models,the focal depths determined by the depth-phase location methods deviate from the real location when there exist large differences between the underground structures and the layered model.In order to improve the accuracy of focal depths and reduce the influence of model errors,we use the fast marching method to solve the eikonal equation and obtain the first P and sPg traveltimes in a heterogeneous model.Then,we conduct earthquake locations by joint inversion of the first P and sPg traveltimes.To validate the proposed method,we conduct synthetic and practical location studies of the 2022 Sichuan Luding MS6.8 earthquake.Results show that the proposed method can improve the accuracy of earthquake location.