基于震源机制解资料的辽宁地区现今构造应力场

近年来,辽宁测震台网不断完善,为通过地震震源机制求解构造应力场提供了比以往更加良好的数据基础。收集并筛选出Global CMT和国内学者文章中1976—2015年、共228份震源机制资料,根据震级大小的不同,对数据赋予相应权重,使用全局网格搜索算法,反演辽宁地区现今构造应力场并给出其不确定范围。研究结果表明:辽宁地区主压应力轴为NEE向,主张应力轴以NNW向为主,在辽西隆起区为近南北向展布;近于1的应力形因子反映出由于西太平洋板块对亚欧板块的NWW向俯冲,导致上地幔软流圈上隆,使辽宁地区整体上处于拉张的应力状态。研究结果及所揭示的构造特征,可对后续研究辽宁地区的地震孕育机制和动力学过程提供参考。

Present Tectonic Stress Field in Liaoning Area Based on Earthquake Focal Mechanisms

The Liaoning Seismic Network has been continuously improved in recent years, which provides a better data basis for solving tectonic stress fields through earthquake focal mechanisms than before. We selected a total of 228 focal mechanisms from Global CMT and domestic publications from 1976 to 2015, weighted the data according to the magnitude of the earthquake, inversed the present tectonic stress field in Liaoning and gave its uncertainty range by the global grid search method. The results show that the principal compressive stress axis of the entire Liaoning region is in NEE direction, and the tensile stress axis is mainly NNW direction, and it is nearly north-south direction in the Western Liaoning uplifts. The stress shape ratio close to 1 reflects that due to the northwest-west subduction of the Eurasian plate by the western Pacific plate, the upper mantle asthenosphere is uplifted, and the Liaoning region is in a state of tension. The results of this study and the tectonic features revealed can provide some reference for the further research on the earthquake preparation mechanism and geodynamic process in Liaoning.