【摘要】 龙门山断裂带位于青藏高原与华南地块之间.由后山断裂、中央断裂、前山断裂和山前隐伏断裂四条主断裂组成.其活动性具有明显的分段性.本文在前人研究成果的基础上,从构造应力的角度对龙门山断裂带的分段性进行分析研究,以茂县-汶川区段和大邑-映秀区段为界将龙门山断裂带划分为三段:北段、中段和南段,且中段是南、北两段的过渡部位.从应力的量值看,龙门山断裂带整体应力状态表现为σH>σh>σv,表明水平应力作用占主导.50～100m深度范围内,北段的应力值明显高于南段.100～200m深度范围内,南段的应力值反而高过北段.且龙门山断裂带南段的应力作用强度高于北段,随深度的增加越发明显.从应力方向看,龙门山断裂带南段最大主压应力方向为NW-NWW向,而北段为NE-NEE向.北、中两段的分界区段应力方向体现了由南段NWW向到北段NEE向转换的特征.应力方向由南到北发生NW向到NE向转变的特征与该区震源机制解反映的主压应力方向较为一致.龙门山断裂带北段受岷山隆起及虎牙断裂影响明显,深部构造或与中南段分离,脱离松潘-甘孜褶皱带的控制,大地震释放的应力比较充分,而南段应力并未充分释放,且震后应力已有一定程度的恢复和重积累,积累能量的程度随深度增加而增强.更多还原

【Abstract】 The longmenshan Fault zone,lies between the Tibetan Plateau and Huanan block,comprises a serial of thrust sheets bounded by four major thrusting faults,i.e.,from west to east the Pingwu-Qingchuan fault,Wenchuan-Maowen fault,Yingxiu-Beichuan fault and Anxian-Guanxian fault.there is a distinct zonation tending the dip of Longmen thrust belt and segmentation along its strike.The previous researches are classified and supplemented with the segmentation in stress state in this paper.On this basis,Longmenshan fault was divided into three segments along its strike,the northern segment,the middle segment and the southern segment.Moreover the middle segment is transition section of the northern segment and the southern segment.Data within 200 m of in-situ stress measurements in 12 boreholes is analyzed.The magnitudes of principle stresses in the northern segment are apparently higher than the ones in the southern segment in depth 50~100 m.The characteristic is reversed in depth 100~200 m.The effect strength of stress in the southern segment is stranger than that in the northern part and is more obvious with depth increasing.Direction of the maximum principle stress in the northern part is NW-NWW,and is NE-NEE in the southern segment.Directions in the boundary segment of the north and the middle present the transfer from NWW to NEE from south to north,in agreement with the orientation characteristic from focal mechanism solutions.The northern section of Longmenshan fault zone is deeply affected by the Minshan uplift and Huya fault,and the deep structures may have separated from the southern section.Stress release in the southern section was not complete and stress has recovered and reaccumulation to a certain degree after the Wenchuan earthquake.更多还原