中文摘要：

在汶川MS8．0级大震发生前一周，采用水压致裂技术在龙门山发震断裂带±400m深度上测得的最大水平主应力值为21－22MPa，与其附近下盘之差高达8～10MPa．大震后的原地重复测量结果表明，发震断裂带上的最大、最小水平主应力值分别降低了29％和23％，而在下盘大震前后的地应力作用状况并无变化．测量结果分析表明，活动断裂带的地应力高值异常是圈定地震危险区的可靠依据，是强震孕育和发生的警示标志．

英文摘要：

One week before the occurrence of Wenchuan Ms8.0 earthquake the maximum horizontal principal stress measured by hydro-fracturing technique in the earthquake Fault of Wenchuan Earthquake （Yingxiu-Beichuan fault） at±400 m depth was 21-22 MPa, which was 8-10 MPa higher than the values measured in the nearby footwall. The repeated measurements after the great earthquake at the same locations indicate that the maximum and minimum horizontal principal stress in the fault belt decreased by 29% and 23% respectively; while in the footwall the stresses did not change after the earthquake. The analysis of the measured result indicates that anomalous high stress in an active fault belt provides a reliable basis for determining the area of high seismic risk, and it is a warning sign of generation and occurrence of strong earthquakes.