山东蓬莱近海岸的地应力状态及断层稳定性评价

为查明蓬莱近海岸的地应力状态，开展了2个钻孔（深度小于200m）的水压致裂地应力测量工作，并与长岛附近海域3个钻孔的地应力状态进行了对比，采用回归分析方法，分析了该地区地应力随深度变化的特征，结合最大剪应力与平均主应力之比（μ_m）和侧压力系数（K'）探讨了研究区的断层稳定性。结果表明:蓬莱近海岸和长岛海域的地应力状态基本一致，最大水平主应力方向主要表现为北东东至东西向，这与华北的区域应力场相一致；水平应力的梯度大于环渤海圈的平均地应力梯度；研究区浅部三向主应力相对大小以S_H > S_h > S_v为主，这有利于逆断层的活动；研究区K'值和μ_m值均较高，分布区间分别为:2.76~3.98和0.47~0.59；陆区断层与区域应力方向均以较大角度相交，处于稳定的状态；海域的北西西向和北东向断层与区域应力场的方向夹角较小，如果区域应力持续增强，将有利于走滑断层的活动，这与震源机制以走滑型地震为主相符。研究结果对研究区内断层稳定性的评价和重大工程的设计及施工都具有重要参考意义。 

THE STATE OF THE IN-SITU STRESS AND FAULT STABILITY EVALUATION OF THE PENGLAI COAST

In order to find out the in-situ stress state near the Penglai coast, hydraulic fracturing in-situ stress measurement was conducted in two boreholes (less than 200 meters in depth). The results were compared with the in-situ stress state of three boreholes off Changdao. Regression analysis was adopted to analyze the variation of in-situ stress with depth in this area. Fault stability in the study area was discussed combined with the ratio (μ_m) of maximum shear stress to average principal stress and lateral pressure coefficient(K'). The results show that the in-situ stress state of the Penglai coast is basically the same with that of Changdao, with the direction of the maximum horizontal principal stress being mainly NEE-EW which is consistent with the regional stress field in north China. The gradient of horizontal stress is greater than the average in-situ stress gradient of Bohai Rim. The relative magnitude of the three-dimensional principal stress in the shallow part of the study area is mainly S_H > S_h > S_v which is conducive to the movements of the reverse faults. The values of both the study area and μ_m are high whose distribution intervals are 2.76~3.98 and 0.47~0.59 respectively. The land area faults and regional stress directions intersect at larger angles and are in a stable state; the angles between the NWW and NE faults of the sea area and the regional stress fields are smaller. If the regional stress continues to increase, it will be conducive to the movements of the strike-slip faults. This may be the primary reason for the frequent earthquakes of Changdao which is consistent with the fact that the focal mechanism of the earthquakes is mainly strike-slip. The research results are of great significance not only to the evaluation of fault stability in the study area but also to the design and construction of major projects.