映秀-北川断裂带中垂直断裂带走向的NW-SE向构造和汶川地震  

The NW-SE-trending Structure Perpendicular to the Yingxiu-Beichuan Faulting Zone and the Wenchuan Earthquake

作　　者：崔军文[1] 王连捷[2] 邹长春[3] 孙东生[2] 彭诚[3] 陈威威[1] 李宗凡 

机构地区：[1]国土资源部大陆动力学重点实验室,中国地质科学院地质研究所,北京100037 [2]中国地质科学院地质力学研究所,北京100081 [3]地下信息探测技术与仪器教育部重点实验室(中国地质大学,北京),北京100083 [4]四川省区域地质调查队,成都610213

出　　处：《地质学报》2016年第6期1041-1061,共21页Acta Geologica Sinica

基　　金：《国土资源部大陆动力学重点实验室》(Key Laboratory of Continental Dynamics,MLR;Institutes of Geology,Chinese Academy of Geological Sciences,Beijing,China)和国家科技专项《汶川地震断裂带科学钻探》(WFSD)项目研究成果

摘　　要：通过汶川科学钻探钻孔地质实体(岩芯)的构造研究、非弹性应变恢复法(ASR法)地应力测试,结合区域构造和汶川地震NW向余震带的综合分析,提出沿映秀-北川断裂走向的狭窄范围内存在一组NW-SE向构造,其总体产状为:走向N48°W,倾角中等,与映秀-北川断裂带的总体走向和ASR地应力测试获得的一组最大主应力方位(侧伏方向224°)和最大水平应力方位(44°)接近垂直。NW-SE向构造,除少数发育为宏观的断裂构造外,多数表现为密集的裂隙系(或隐断裂)和隐伏断裂,以逆冲性质为主,局部略具左行走滑特征。映秀-北川断裂两侧相向倾斜的NW-SE向裂隙系表明其两侧存在有方向相反的运动,映秀-北川断裂属两侧具有不同形成机制和相向位移的双侧走滑型断裂。映秀-北川断裂的同震垂向位移受NE-SW向构造和NW-SE向构造双重因素制约,在汶川地震的主震带与NW向余震带叠置部位具最大的垂向位移量。从时间尺度分析,在汶川地震的全过程中,仅开始时刻表现为自NW→SE方向的强烈逆冲作用,随后的主要时间段内均表现为沿断裂带方向的运动和自SW→NE方向的逆冲。NW-SE向构造的形成是龙门山深部应力和能量长期积聚的结果,强震发生时,初始时刻的自NW向SE方向的强烈挤压,瞬即转换成自SW向NE方向的运动和强烈挤压。NE-SW向挤压构造应力场,是由NW-SE向挤压作用长期积累和诱导,并叠置在区域NW-SE向主导的挤压构造应力场之上的局部构造应力场,但在发震后,它主导了地震能量自震源区沿断裂走向向NE方向的快速传递和扩展及NW向强余震的发生,地震能量在NE-SW向强烈挤压过程中得到最终释放。因此,映秀-北川断裂在地震的不同阶段,其性质存在差异,在地震宁静期或弱震期(应力积累和闭锁期)以自NW往SE方向的逆冲性质为主,兼有右行走滑特征,但在强震期(应力释放和解锁期),除发震时表现为�Based on study of the geological entities（core）using the Wenchuan Scientific Drilling hole（WFSD）,anelastic strain recovery（ASR）stress measurements,analysis of the regional tectonic and distribution of the Wenchuan earthquake NW-trending aftershocks,this study suggests that one group of NW-SE structures with striking N48°W and moderate dipping occur within the narrow range of the YingxiuBeichuan fault.Its striking is generally parallel to the directions of Yingxiu-Beichuan fault zone and the maximum main stress using AS stress measurement,and approximately perpendicular to the orientation（44°）of the maximum horizontal stress.Most of the NW-SE-trending structure,except several macro faulting,show more densed fractures（or hidden fractures）,which are dominated by thrusting,with characteristic of locally slightly left-lateral strike-slip.NW-SE-trending fracture system on both sides of the Yingxiu-Beichuan fault indicate that the Yingxiu-Beichuan fault belongs to bilateral strike-slip type fault,both sides of which have different formation mechanism and the opposing displacement.The vertical displacement of the Yingxiu-Beichuan fault is controlled by the NE-SW trending structures and the NW-SE structure.The superimposed part between the NE main shock zone and NW-trending aftershocks zone is of the maximum vertical displacement amount.From the analysis of time scale,during the whole process of the Wenchuan earthquake,only initial moment was expressed by strong NW-SE-trending thrusting,followed by movement along the faulting direction and trusting from SE to NE during the main stage of time.NW-SE-trending structure was the result of deep stress and energy accumulation at the Lonmenshan.When the earthquake hitting,the initial NW-SE-direction compression started and instantly turned to strong SW-NE-direction compression.NE-SW-trending compressional tectonic stress field was a regional tectonic stress,which was superimposed over regionally NW-SE-trending compressive tectonic belt due to long-term accum

关 键 词：汶川地震 映秀-北川断裂 汶川地震断裂带科学钻探(WFSD) NW-SE向主导挤压构造应力场 地质实体 NW-SE向构造 NE-SW向局部挤压构造应力场 

分 类 号：P315.2[天文地球—地震学]