郯庐断裂带中南段闭锁特征与地震危险性分析

利用华北地区1999～2007、2013～2017两期GPS水平运动速度场数据,采用块体负位错模型,分别反演了郯庐断裂带中南段不同段的断层闭锁程度和滑动亏损速率分布;结合地表应变结果,综合分析了郯庐断裂带前后两期的变形差异特征,并探讨了其与日本3·11地震间的可能关系。研究结果表明:日本地震后,郯庐断裂带中南段郯城以北的段落闭锁程度有所减弱,中南段东部地区主张应变率增强,处于拉张状态;日本大地震的发生对郯庐断裂带中南段的应变积累起到一定的缓解作用。2013～2017最新一期反演结果显示莒县以北断层闭锁程度仍较高,闭锁深度较深,为右旋挤压亏损,是1668年郯城地震的未破裂段;莒县以南到泗洪附近断层闭锁程度较低,无滑动亏损积累;泗洪以南到嘉山段断层闭锁程度较高,是历史地震的未破裂段,同时该地区小震不活跃,易于应力积累,地震危险性值得关注。

Fault blocking characteristics and seismic hazard analysis in the middle and southern segments of the Tanlu Fault Zone

In this paper, we employ the back- slip dislocation model to invert the distribution of fault coupling and slip rate deficit on the different segments of the Tanlu fault zone, according to the GPS- derived horizontal velocity field data of 1999~2007 and 2013~2017 in North China. Combining the deformation characteristics following the two periods, we discuss the possible relationship between the deformation characteristics with the Japan 3·11 Tohoku earthquake. The results show that the coupling rate reduces in the north of Tancheng County on the middle- south segments of the fault following the earthquake; and meanwhile the principal extensional strain rate increases in the eastern part, suggesting the strain release in the middle and south segments following the earthquake. The inversion derived from the 2013~2017 data shows that the north segment of Juxian still has the high coupling rate, the deep blocking depth, and the dextral compressive deficit, which is the unrupture section of the 1668 Tancheng earthquake. The coupling rate is low from south of Juxian County to the vicinity of Sihong, and there is no slip deficit accumulation. From south of the Sihong to Jiashan segment, the coupling rate is higher, which is the unrupture section of the Tancheng earthquake. More importantly, the seismic hazard should pay more attention as the sparse micro- seismicity, which is beneficial to accumulate the stress.