| 北京地区地应力测量与主要断裂稳定性分析 |
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| 引用本文： | 秦向辉,张鹏,丰成君,孙炜锋,谭成轩,陈群策,彭有如.北京地区地应力测量与主要断裂稳定性分析[J].地球物理学报,2014,57(7):2165-2180. |
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| 作者姓名： | 秦向辉 张鹏 丰成君 孙炜锋 谭成轩 陈群策 彭有如 |
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| 作者单位： | 1. 中国地质科学院地质力学研究所, 北京 100081;2. 国土资源部新构造运动与地质灾害重点实验室, 北京 100081;3. 北京市地质工程设计研究院, 北京 101500 |
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| 基金项目： | 中国地质调查局项目“北京地区主要活动断裂工程地质稳定性评价与地应力测量”(1212010814052);中国地质调查局项目“首都圈地区关键构造部位深孔地应力测量监测与地质安全评价”(12120113012100);深部探测技术与实验研究专项(Sinoprobe-06-03);中国地质科学院地质力学研究所基本科研业务费项目(DZLXSJK201107)联合资助 |
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| 摘 要： | 2008年汶川地震后，为查明北京地区现今地应力状态、评价断裂稳定性，相继在北京地区开展了5个深孔（600~1000 m）的水压致裂法地应力测量，并在适宜深度安装了地应力相对变化监测探头，建立了地应力变化监测台站.本文首先利用实测地应力数据分析了北京地区地壳浅表层应力状态，结果表明：（1）北京地区千米深度内，最大、最小水平主应力随深度增加梯度系数分别为0.0328和0.0221，侧压系数Kav和KHv值，最大、最小水平主应力之比KHh值与国内外已有认识基本一致，而水平向剪应力相对强度参数μm值较低;（2）北京地区最大水平主应力优势方向为近EW向，与华北地区构造应力场方向基本一致，同时受区内断裂活动等影响，存在与区域主应力方向偏差的局部应力场;（3）实测数据揭示的应力结构显示，北京地区地壳浅表层最大主应力（σ1）总体为最大水平主应力（σH），受区域构造演化以及测点附近断裂的影响，中间主应力（σ2）与最小主应力（σ3）所对应的实测地应力存在变化，但总体来讲，实测地应力数据揭示的应力结构与北京地区主要断裂性质基本相吻合.其次，基于实测应力数据，采用库仑摩擦滑动准则，结合拜尔定律，并取摩擦系数为0.2~1.0，初步评价了北京地区主要断裂稳定性，结果显示：（1）在摩擦系数取0.6~1.0条件下，北京地区现今应力状态尚未达到导致断裂失稳滑动水平，断裂不会出现失稳滑动现象;（2）摩擦系数弱化到0.4时，西峰寺钻孔应力状态满足断裂失稳滑动条件，揭示出八宝山断裂存在失稳滑动可能性，而夏垫-马坊断裂和黄庄-高丽营断裂附近测点应力状态将趋近满足断裂失稳滑动条件，表明这两条断裂有趋向失稳滑动可能性;（3）只有当摩擦系数弱化到0.2时，北京地区主要断裂才可能在现今应力状态出现断裂失稳滑动.本文的认识对北京地区乃至华北地区构造应力场、地震地质研究有重要参考意义.
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| 关 键 词： | 北京地区 地应力 水压致裂法 地壳应力状态 库仑滑动摩擦准则 断裂稳定性 |
| 收稿时间： | 2013-09-24 |
In-situ stress measurements and slip stability of major faults in Beijing region,China |
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| QIN Xiang-Hui,ZHANG Peng,FENG Cheng-Jun,SUN Wei-Feng,TAN Cheng-Xuan,CHEN Qun-Ce,PENG You-Ru.In-situ stress measurements and slip stability of major faults in Beijing region,China[J].Chinese Journal of Geophysics,2014,57(7):2165-2180. |
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| Authors: | QIN Xiang-Hui ZHANG Peng FENG Cheng-Jun SUN Wei-Feng TAN Cheng-Xuan CHEN Qun-Ce PENG You-Ru |
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| Institution: | 1. Institute of Geomechanics, Chinese Academy of Geological Sciences (CAGS), Beijing 100081, China;2. Key Laboratory of Neotectonic Movement & Geohazard, Ministry of Land and Resources, Beijing 100081, China;3. Beijing Design Institute of Geological Engineering, Beijing 101500, China |
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| Abstract: | In order to estimate the upper crustal stress state and slip stability of major faults after the Wenchuan MS8.0 earthquake, five boreholes, i.e., Pinggu, Shisanling, Xifengsi, Miyun, and Lisiguang Memorial Hall borehole ranging from 600 to 1000 m were drilled in Beijing region. Hydraulic fracturing method was used to conduct in-situ stress measurements in these five boreholes, and stress monitoring equipment was installed at appropriate depth and monitoring stations were constructed. Those data derived from the in-situ stress measurements reveal that the gradient coefficients of the maximum horizontal stresses and minimum horizontal stresses versus depth are 0.0328 and 0.0221, respectively; and the magnitudes of lateral pressure coefficient such as Kav, KHv and the ratios (KHh) of the maximum horizontal stress to minimum horizontal stress are consistent with previous studies. However, the ratios (μm) of the maximum horizontal shear stress to the average horizontal stress are relatively low. It is noted that the dominant direction of the maximum horizontal stress in Beijing region is ~EW which is the same with the tectonic stress field of North China. However, sub-regional stress field induced by faults which shows deviation from the orientation of North China, has been also revealed. In addition, the stress regimes inferred from in-situ stress data imply that the maximum horizontal stress (σH) is the maximum principal stress (σ1), while the intermediate (σ2) and the minimum principal stress (σ3) show some variations. It is suggested that these variations may be caused mainly by the regional tectonic evolution and the activity of faults near the boreholes. Based on these characteristic parameters, we can point out that the maximum horizontal stress in the upper crust of Beijing region can be defined as dominant stress, while the horizontal shearing stress is relatively weak. Finally, slip stability of major faults in Beijing region is estimated according to Column friction criterion and Byerlee's law, together with the frictional coefficients being assumed to be 0.2, 0.4, 0.6 and 1.0. The results reveal that when the frictional coefficient ranges from 0.6 to 1.0, the recent crustal stress state of Beijing region does not yet reach the expected limit of fault slip. The stress values of the Xifengsi borehole will reach the expected limit when the frictional coefficient is weakened to 0.4, revealing that the Babaoshan fault stands chance of slipping; the Xiadian-Mafang fault and the Huangzhuang-Gaoliying fault will approach to the expected limit of slip and will stand chance of slipping under this hypothesis, but only with very low possibility. However, it should be pointed out that if the frictional coefficient is weakened to as low as 0.2, the major faults in Beijing region will be unstable and slip may occur under the present-day crustal stress state. Conclusions in this paper would be of great significance for studies on tectonic stress field and seismogeology in Beijing region, even North China. |
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| Keywords: | Beijing region In-situ stress Hydraulic fracturing Crustal stress state Column frictional failure criterion Fault slip stability |
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