九寨沟M_S7.0地震前跨断层水准前兆异常与震后变化

Precursory Anomalies of Across-Fault Leveling before the Jiuzhaigou M_S7.0 Earthquake and Variation after the Quake

利用2017-08-08九寨沟MS7.0地震前震区北侧青藏块体东北缘跨断层短水准观测资料,以及震后8月、9月两期加密复测结果,综合观测曲线、异常时空演化特征及特征强度指标,分析九寨沟地震前断层形变异常及震后变化。结果显示,九寨沟地震前1a多西秦岭至六盘山构造区异常比较集中;震前1～3个月西秦岭构造区及其附近(震区周边300km范围内)短期异常增多,异常特性以逆断性突跳为主,对该次地震有中短期-短期前兆反映;震后1个月西秦岭构造区多数异常调整恢复。

In this paper,the anomalies of fault deformation before the Aug.8th,2017 Jiuzhaigou M S 7.0 earthquake,and their variations after the quake,are analyzed.We use the data of across-fault short-leveling at the northeastern margin of Qinghai-Xizang block,together with added data observed in August and September after the quake,with the aid of observational curves and time-space evolution of the anomalies,as well as the index of feature intensity.The results show that:Over one year before the earthquake,the anomalies are relatively concentrated at the area from western Qinling to Liupanshan tectonic region;1-3 months before the earthquake,short-term anomalies at the western Qinling tectonic region and nearby display an increasing trend within the distance of 300 km of the epicenter;this mainly reveals abrupt thrust change characteristics,which have medium-short-term and short-term precursory features;one month after this earthquake,most anomalies had adjusted and recovered.