Focal mechanisms of recent small and moderate earthquakes in Liaoning region

In this study, we use the CAP method to determine the focal mechanisms of 19 earthquakes of magnitudes 3.5 and above in Liaoning Province, China from 2013 to 2017. Results show that earthquakes in Liaoning are predominantly strike-slip, with most of the P- and T-axes oriented in ENE and NNW directions, respectively, consistent with the maximum compressional and extensional axes of the regional tectonic stress field of northeast China. The centroid depths of the earthquakes are distributed in the whole crust, with most in the mid crust. There are extremely shallow moderate earthquakes in the Dengta area, which calls for immediate attention in earthquake disaster prevention efforts. There are also earthquakes near the bottom of the crust in Gaizhou area, indicating that the rocks there still behave in a brittle fashion. Being in the vicinity of an active block boundary, earthquakes near Gaizhou can occur near the bottom of the crust where faults cut through the entire crust. Our results suggest that regional tectonic stress field plays a dominant role in most earthquakes in Liaoning, while in some local areas the complex fault structure may also significantly influence the focal mechanisms.