2015年金口河M_S5.0级地震前地应力状态及动力学背景分析  

Analysis of in-situ stress state and dynamic background before the 2015 Jinkouhe M_S5.0 earthquake

作　　者：李兵[1,2] 丁立丰[2] 郭启良[2] 姜大伟[2] 谢富仁[2] LI Bing;DING Lifeng;GUO Qiliang;JIANG Dawei;XIE Furen(Schoolof Earth and Space Sciences,University of Science and Technology of China,Hefei,Anhni,230026,China;Institute of Crustal Dynamics,China Earthquake Administration,Beijing,100085,China)

机构地区：[1]中国科学技术大学,地球和空间科学学院,合肥230026 [2]中国地震局,地壳应力研究所,北京100085

出　　处：《地质学报》2020年第8期2500-2508,共9页Acta Geologica Sinica

基　　金：中国地震局地壳应力研究所中央级公益性科研院所基本科研业务专项资助项目(ZDJ2019-20);国家科技支撑计划课题:地震应力环境探测技术与方法研究(2012BAK19B03);国家自然科学基金项目(编号41802226)项目资助的成果。

摘　　要：2015年金口河发生了M_S5.0级地震,为揭示地震与地应力的内在关系和动力学背景,对距震中约12km的2个钻孔的水压致裂地应力测量资料进行了分析研究,利用拜尔利准则和应力莫尔圆分析了峨边-金阳断裂带北部断层的稳定性,并结合地震活动性参数b值探讨了金口河地震发生的动力学背景。研究结果表明:在钻孔94.90~722.10 m的深度内,最大水平主应力为5.89~14.50 MPa,最小水平主应力在3.79~10.30 MPa,应力水平较低;最大水平主应力方向在N50°W^N68°W,趋于北西至北西西向,与区域构造应力场一致;YJP-1孔三向主应力的相对大小表现为有利于逆断层和走滑断层的活动,DPS-1孔三向主应力的相对大小表现为有利于正断层的活动;DPS-1孔有效应力条件下的μ_m(最大剪应力与平均应力之比)平均值为0.46,已接近断层摩擦滑动临界值下限0.51,有利于正断层的滑动;峨眉-烟峰断层弯曲构造部位应力闭锁集中区,是导致钻孔附近水平构作用较弱的主要原因。研究结果对于揭示金口河M_S5.0级地震前的动力背景具有重要意义。An M_S5.0 earthquake occurred in Jinkouhe in 2015. In order to reveal the internal relationship and dynamic background between the earthquake and the in-situ stress, the in-situ stress measurement data of hydraulic fracturing in two boreholes about 12 km away from the epicenter were analyzed and studied, the stability of faults in the northern Ebian-Jinyang fault zone is analyzed by using by Byeerly’s criterion and stress Mohr’s circle, and the dynamic background of the occurrence of the Jinkouhe earthquake is discussed in combination with the value of seismicity parameter b. The results show that, within the depth of 94.90 to 722.10 meters, the maximum horizontal principal stress is 5.89 MPa to14.50 MPa, and the minimum horizontal principal stress is 3.79 to 10.30 MPa;that the maximum horizontal principal stress direction is N50° W to N68° W, which tends to be Northwest to West direction, consistent with the regional tectonic stress field;that the relative magnitude of the triaxial principal stress of YJP-1 borehole is favorable for the activities of reverse fault and strike-slip fault, while the relative magnitude of the triaxial principal stress of DPS-1 borehole is favorable for the activities of normal fault;that the average value of μ_m(ratio of maximum shear stress to average stress) under the effective stress condition of DPS-1 borehole is 0.46, which is close to the lower limit of fault friction sliding threshold of 0.51, and is favorable for normal fault sliding, and that the stress locking concentrated area in the bending structure of Emei-Yanfeng fault is the main reason for the weak horizontal structure near the borehole. The research results are of great significance for revealing the dynamic background before the Jinkouhe M_S5.0 earthquake.

关 键 词：金口河M_S5.0级地震 峨边-金阳断裂带 地应力状态 Byerlee准则 断层稳定性 地震活动性参数b值 

分 类 号：P315[天文地球—地震学]