Multi-Method Study on Seismogenic Structure of Rushan Earthquake Sequence in Shandong Province, China

The M L 3.8 earthquake occurred in Rushan County On October 1, 2013, Shandong Province, eastern China. After this event, there are already more than 19 600 seismic events recorded by digital seismic seismographs, forming an earthquake sequence. Although three moderate and strong earthquakes occurred successively during this period, the surface rupture undiscovered, it is difficult to diagnose the seismogenic fault from the geological perspective. However, the 3-D velocity structure inversion can provide important information on the location of the moderate earthquakes of the source area, which can help to understand the formation of earthquakes. Compared with source locations, the focal mechanisms can visually reflect the geometric and kinematic characteristics of seismogenic fault rupture, being the basis for inferring the regional tectonic stress field. Moreover, changing the stress field will affect the geometric parameters of the crack and change the shear-wave splitting parameters. Therefore, it is of great significance to explore the processes of earthquakes and the seismogenic mechanisms utilizing the spatiotemporal variation of shear wave splitting parameters. In summary, we comprehensively analyzed the seismogenic fault of the Rushan earthquake sequence (RES) with the help of the above methods. The resluts showed that the seismogenic fault of RES is towards the NWW-SEE direction and dips towards the southwest, dominated by high-angle strike-slip movements with certain thrust dip-slip components.