辽宁地区近期中小地震震源机制研究

本研究利用CAP方法反演得到了2013—2017年辽宁地区19个3.5级以上地震的震源机制解.结果显示辽宁地区地震的震源机制以走滑类型为主，P轴和T轴方位分别集中在北东东和北北西方向，分别与区域构造应力场主压和主张应力方向一致.矩心深度结果反映辽宁地区在地壳内各个深度的位置都可能孕震，而以地壳中部最为活跃.灯塔地区地壳极浅部曾发生中等强度的地震，在地震减灾工作中需要引起注意.而盖州地区地壳底部仍有少量地震，显示其附近岩石仍具有脆性特性，且该处邻近一级块体边界，贯穿地壳的断层导致下地壳也有地震发生.震源机制结果显示区域构造应力场对辽宁地区大部分地震的发生有着主导作用，在局部地区复杂的断层构造也会对震源机制产生较大影响.

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.