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2013年芦山M_S7.0地震前,康定台基岩地温、鲜水河跨断层形变和姑咱台钻孔应变都显示沿鲜水河断裂带可能存在区域应力变化。文中选取鲜水河断裂带基岩地温观测网3个台的观测数据开展进一步分析,并与钻孔应变等对比研究。结果显示,3个基岩地温观测台站的应力温度在芦山地震前几天出现同步突降,反映鲜水河断裂带乾宁—康定一带区域应力拉张增强。3个台站基岩地温的高频成分在震前80d内也出现了同步变化,估算出的应力变化范围为0.98~1.96MPa,平均约1.47MPa,与测震学获得的芦山地震(剪)应力降结果接近。基岩地温显示的区域应力拉张增强与姑咱钻孔应变的张性突变一致,而与跨断层形变监测结果对比则显示鲜水河断裂带不同活动段在芦山地震前不同时间段的应力变化不尽相同,但都显示芦山地震前沿鲜水河断裂带存在区域应力变化。
Prior to the Lushan M_S7.0 earthquake in Lushan in 2013, the geothermal bedrock of Kangdingtai, the cross-fault deformation of Xianshuihe and the borehole strain of Guanshi showed the possible regional stress changes along the Xianshuihe fault zone. In this paper, the observation data of three stations of bedrock geothermometer in Xianshuihe fault zone are selected for further analysis and compared with the drilling strain. The results show that the stress temperature of the three bedrock geothermal observatories synchronously collapses a few days before the Lushan earthquake, which indicates that the stress tension in the Qianning-Kangding area of the Xianshuihe fault zone is enhanced. The high-frequency components of bedrock temperature also appeared synchronous within 80 days before the earthquake, and the estimated stress ranged from 0.98 to 1.96 MPa with an average of 1.47 MPa. Compared with the Lushan earthquake (shear) The result of stress drop is close. Compared with the results of cross-fault deformation monitoring, the regional tensile stress enhancement of bedrock ground temperature is consistent with that of Guanshan drilling strain. The stress variation of different active segments of Xianshuihe fault zone at different time periods before Lushan earthquake But they all show the regional stress changes in the Xianshuihe fault zone along the front of the Lushan earthquake.