构造转换区强震间相互作用机制的数值模拟研究:以2008—2020年4次M_(S)>6.0于田地震为例  

Interaction mechanism of strong earthquakes in the tectonic transition zone:a numerical study of four M_S>6.0 Yutian earthquakes from 2008 to 2020

作　　者：刘雷 李玉江 季灵运[1] LIU Lei;LI YuJiang;JI LingYun(The Second Crust Monitoring and Application Center,China Earthquake Administration,Xi'an 710054,China;National Institute of Natural Hazards,Ministry of Emergency Management,Beijing 100085,China)

机构地区：[1]中国地震局第二监测中心,西安710054 [2]应急管理部国家自然灾害防治研究院,北京100085

出　　处：《地球物理学报》2024年第1期156-171,共16页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(42274138,42104061);陕西省自然科学基础研究计划项目(2021JQ-979);中国地震局地震科技星火计划项目(XH23059YA)资助。

摘　　要：2008年于田M_(S)7.3地震后,阿尔金断裂带西南段的构造转换区内接连发生了2012年M_(S)6.2、2014年M_(S)7.3和2020年M_(S)6.4等强震.研究强震间相互作用对于理解强震的发震机制具有重要意义.本文通过构建阿尔金断裂西南段及邻区三维黏弹性有限元模型,以强震同震滑动模型为约束,综合同震位错与震后黏弹性松弛效应的影响,研究4次强震间相互作用以及强震发生所引起的区域内断裂库仑应力变化.计算结果表明:考虑同震和震后效应的共同作用,后续3次地震发生前震源处库仑应力变化分别为-1.89×10~4 Pa、3.63×10~4 Pa和1.04×10~4 Pa,表明2008年于田地震延迟了2012年于田地震的发生,2008和2012年于田地震共同触发了2014年于田地震的发生,而前3次地震同样触发了2020年于田地震的发生.从不同构造部位强震间相互作用的结果来看,阿尔金断裂西南段尾端张性区内发生的正断型强震,对区域内北东向断层上的左旋走滑型强震有加载效应,造成强震的提前发生,同时也会延迟尾端张性区内近南北向的断层上正断型强震的发生.综合分析认为,阿尔金断裂和郭扎措断裂西段应力显著增加(>1.0×10~5 Pa),未来发生强震的可能性很高,需要重点关注.Following the 2008 Yutian M_S7.3 earthquake,strong earthquakes such as M_S6.2 in 2012,M_S7.3 in 2014,and M_S6.4 in 2020 occurred successively in the tectonic transition zone that located at the southwestern segment of the Altyn Tagh fault zone.Seismic interaction provides the key to understanding the mechanism of earthquakes.In this study,we construct a three-dimensional viscoelastic finite element model of the southwestern segment of the Altyn Tagh fault and its adjacent region,to analyze the interaction between four strong earthquakes,and further calculate the co-and combined(co-plus post-seismic)Coulomb stress change of the faults caused by these strong earthquakes,with the co-seismic slip model as constraints.The results show that the combined Coulomb stress change before the occurrence of the subsequent three earthquakes are-1.89×10~4 Pa,3.63×10~4 Pa,and 1.04×10~4 Pa,respectively,indicating that the 2008 Yutian earthquake delayed the occurrence of the 2012 Yutian earthquake,while the 2008 and 2012 Yutian earthquakes jointly triggered the 2014 Yutian earthquake,and also the three earthquakes advanced the 2020 Yutian earthquake.Meanwhile,stress transfer between strong earthquakes at different tectonic locations shows that earthquakes in the extensional area at the end of the southwestern segment of the Altyn Tagh fault cast a positive effect to the event on the NE-trending sinistral strike-slip fault,which advances the occurrence of it.On the contrary,it also delays the occurrence of strong earthquakes on the nearly NS-trending normal fault in the extensional area of the southwestern segment end of the Altyn Tagh fault.Comprehensive analysis shows that the Altyn Tagh fault and the west segment of the Gozha Co fault experience a significant stress increase(>1.0×10~5 Pa),and more attention should be paid to the seismic hazard.

关 键 词：于田地震 同震滑动分布 有限元模拟 库仑应力变化 地震危险性 

分 类 号：P313[天文地球—固体地球物理学] P315[天文地球—地球物理学]