Initial Rupture Depth of the 8 August 2017 M7. 0 Jiuzhaigou Earthquake Derived from Pn/Pg Relative Location

We used the Pn/Pg relative location method to locate the initial rupture depth of the Jiuzhaigou M7. 0 earthquake and some aftershocks. Due to sparse seismograph network and complex three-dimensional crustal velocity structure, it is difficult to accurately determine this parameter by the traditional seismic arrival-time location method. In this study, we measured the hypocenter location of August 10, 2017 M4. 1 aftershock and 7 November 2017 M4. 5 aftershock with portable seismographic observation records, and selected them as reference events. Then we used Pg phase to adjust the horizontal location and Pn phase to determine the hypocentral depth. The influence of the velocity model was reduced effectively using the Pn/Pg relative location method. The results show that the initial rupture depth of the main shock is about 9 km, and the aftershocks are distributed at 7 similar to 13 km depths, mainly in the vicinity of the hypocentral depth of the main shock.