跨断层“点-线-面”研究方法及在震例分析中的应用

基于青藏高原东北缘地区跨断层短水准资料, 采用形变异常强度、 断层合成速率和断层形变趋势累积等多种研究方法, 利用“点-线-面”相结合的研究思路, 全面分析了2013年岷县漳县M_S6.6地震前的应变背景、 断层活动和短期形变特征。 结果显示: ① 该地震处于垂直形变累积率的高值区, 应变积累程度较高; ② 断裂带之间存在显著的运动差异, 发震断裂震前中短期运动速率显著增强, 并造成区域运动的不均衡, 西秦岭局部地区应变积累增加; ③ 随着强震的逼近, 震前显著异常场地分布明显向近震区迁移和集中, 且异常强度也随之增大。 以上结果对强震发生危险地点和发生时间有短期指示意义, 因此, “点-线-面”相结合的研究方法有利于认识地震前兆信息, 对地震孕育背景判定及地震危险性分析具有重要意义。

Cross-fault Point-Line-Area Analysis Method and its Application in Earthquake Case Study

Based on across-fault short leveling data of the northeastern margin of Qinghai-Tibet Plateau, combined with calculation methods such as deformation anomaly intensity, deformation synthetic rate and deformation trend accumulation rate, and the adopted research thought of combining of point, line and area, we comprehensively analyzed strain background, fault activity and short-term deformation characteristics before the 2013 Minxian-Zhangxian M6.6 earthquake. The results show that: ① This earthquake occurred in the period of the vertical deformation rate at a high value and high degree of strain accumulation; ② The medium-term movement rate significantly increased in the seismogenic fault and there was a significant differential movement between the faults, which caused regional imbalance of motion and strain accumulation of western Qinling area; ③ With the approximation of earthquake, significant anomaly fields migrated and concentrated to the near-source area and abnormal level also increased. These results have short-term instruction for the prediction of earthquake’s location and occurrence time. In conclusion, the combination of point-line-area research method is beneficial to understand earthquake precursor information, and would be of importance in the judgment of seismogenic background and analysis of seismic hazard.