九寨沟MS7.0地震前跨断层水准前兆异常与震后变化

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1 a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300 km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。

Precursory Anomalies of Across-Fault Leveling before the Jiuzhaigou MS7.0 Earthquake and Variation after the Quake

In this paper, the anomalies of fault deformation before the Aug. 8th, 2017 Jiuzhaigou MS7.0 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.