【摘要】 汉中盆地位于龙门山断裂带东北段的末端,汶川MS8.0地震发生以后,地震活动存在沿龙门山断裂带向NE向发展的趋势.在汉中盆地西缘进行了两个钻孔的水压致裂地应力测量,来分析震后该区地应力状态,以期为该区的地震危险性研究提供实际资料.这两个钻孔深度均为300m左右,相距33m,取得了较好的地应力测试结果.通过对地应力测试结果的综合分析研究,得到以下认识:①在汉中盆地西缘300m深度地层内,最大水平主应力值为5.69—19.52MPa,最小水平主应力值为3.81—10.90 MPa,垂直主应力值约为1.25—7.03MPa,水平主应力占主导地位,垂直应力为最小应力,该地应力状态有利于逆断层的活动;②汉中盆地西部现今最大水平主应力方向为WNW或近EW向;③汶川地震后,目前汉中盆地及其西部地区仍处于构造应力调整阶段,总体相对稳定.更多还原

【Abstract】 Hanzhong basin is located at the end of northeastern section of Longmenshan fault zone.After the Wenchuan MS8.0earthquake,the earthquakes tend to occur mainly in the northeastern section of the Longmenshan fault and migrate towards NE direction.In order to study the stress state after the mainshock and analyze the seismic risk in Hanzhong basin region,two drillings were arranged to conduct hydrofracturing in-situ stress measurement on the western margin of Hanzhong basin.Both drillings have a depth of 300m,the distance between the two drillings is 33m.The results of stress measurement are perfect.Based on a comprehensive analysis of the stress measurement results,the following conclusions are drawn:① On western margin of Hanzhong basin within 300mdepth,the maximum horizontal principal stress is 5.69—19.52MPa,the minimum horizontal principal stress is 3.81—10.90 MPa,and the vertical principal stress is 1.25—7.03 MPa.The horizontal principal stress plays a dominant role and the minimum principal stress is vertical.The stress state is in favor of thrust fault movement.② The present maximum horizontal principal stress in Hanzhong basin is in WNW--ESE orientation or in EW.③ Since the occurrence of Wenchuan MS8.0earthquake,the tectonic stress in Hanzhong basin and its western neighbour region has been in an adjustment phase and being stable generally.更多还原