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川甘陕交汇地区新构造活动强烈、地震频发,具有复杂多样的构造变形模式和构造强烈活动特征,为一潜在地震危险性研究的关键构造部位。为了查明川甘陕交汇关键构造部位地壳浅表层现今地应力环境和潜在地震危险性,在甘肃省水市甘谷县及四川省广元市三堆镇实施机械岩心钻探工程和水压致裂地应力测量。地应力测量结果表明,甘谷钻孔3个主应力关系为SH>Sh>Sv,甘谷地区现今水平主应力起主导作用,且具有较高地应力值,钻孔附近最大水平主压应力方位平均为N41°E,易于钻孔附近北西西向西秦岭北缘断裂产生左旋走滑兼逆冲活动;三堆钻孔3个主应力关系为SH>Sh>Sv,该地区现今水平主应力起主导作用,钻孔附近最大水平主压应力方位平均为N85°W,利于钻孔附近北东向青川断裂产生右旋走滑兼逆冲活动。利用库仑摩擦滑动准则对断裂活动进行分析,结果表明天水和广元地区的地应力大小均已经达到了使地壳浅部断层产生滑动失稳的临界条件,需加强地应力实时监测和分析。该研究成果为川甘陕交汇关键构造部位的断裂活动性分析和地质环境安全评价提供科学依据。
The neotectonic activity in the junction of Sichuan, Gansu and Shaanxi provinces is intense with frequent earthquakes, with complex and diverse tectonic deformation patterns and strong tectonic activities, which are the key tectonic parts of a potential seismic hazard study. In order to find out the current geostress environment and potential earthquake risk of the shallow crust of the key tectonic parts of the intersection of Sichuan, Gansu and Shaanxi, mechanical core drilling and hydraulic fracturing in-situ stress measurement were carried out in Gangu County, Gansu Province, Shuibang of Gansu Province and in Sandui Town, Guangyuan City, Sichuan Province . The results of in-situ stress measurements show that the three principal stress relations of Gangu drilling are SH> Sh> Sv, the main horizontal stress in Gangu area plays a leading role and high stress values, and the average principal compressive stress azimuth of the maximum horizontal near borehole is N41 ° E, left-lateral strike-slip and thrusting activities are induced in the northwestern margin of the NW from west to north of the vicinity of the borehole. The three principal stress relationships of the three heaps are SH> Sh> Sv. Nowadays, the horizontal principal stress plays a leading role in drilling The maximum horizontal compressive stress azimuth near the hole is averagely N85 ° W, which is conducive to the dextral strike-slip and thrusting movement of the northeast Qingchuan fault near the borehole. The Coulomb frictional sliding criterion is used to analyze the fault activity. The results show that the geostress of Tianshui and Guangyuan areas have reached the critical conditions for sliding instability of shallow crustal faults, and the real-time monitoring and analysis of ground stress should be strengthened. The research results provide a scientific basis for fault activity analysis and geo-environmental safety assessment of the key tectonic parts of the junction of Sichuan, Gansu and Shaanxi provinces.