Abstract:
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摘要 2013年芦山MS7.0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。
Abstract:Before 2013 Lushan MS7.0
earthquake, the bedrock ground temperature in Kangding station, the
cross-fault deformation and the borehole strain in Guza station all show
that regional stress changes possibly occurred along the Xianshuihe
Fault. In this paper, further analysis is made on the observation data
of bedrock ground temperature in the three stations in the Xianshuihe
fault zone, and the results are compared with borehole strain,
seismometry and cross-fault deformation data. Stress temperature in the
three stations dropped suddenly synchronously a few days before the
Lushan earthquake, indicating the enhanced tension characteristics of
the regional stress in the Qianning-Kangding zone. High-frequency
components of bedrock temperature in the three stations also showed
synchronous changes in the 80 days before the Lushan earthquake, with an
estimated stress change range of 0.98~1.96MPa, an average of about
1.47MPa, which is close to the seismometry results. Besides, tensional
mutation in borehole strain is consistent with the enhanced tensional
characteristics of regional stress revealed by bedrock ground
temperature. Comparison with cross-fault deformation shows that the
stress change was different in different active segments of the
Xianshuihe Fault in different time periods before the Lushan earthquake,
but the regional stress change did appear along the Xianshuihe fault
zone before the Lushan earthquake.
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