结合钻孔水位、GPS资料分析2016年门源MS6.4地震前分量钻孔应变异常特征

Anomaly Characteristics of 4-component Borehole Strain Analyzed Jointly with Borehole Water Level and GPS Data before the 2016 Menyuan M_S6. 4 Earthquake

针对青海门源台分量钻孔应变观测,从不同观测频段角度进行异常分析,结果表明在2012年下半年挤压应力增强的背景下,各频段分别表现出大幅压缩异常、潮汐因子时空演化以及高频异常信息增强的现象。同钻孔的水位观测也表现出在挤压应力作用下流体向外逃逸、水位下降的现象。而跨区域主要构造的GPS站速度剖面结果也反映了2013年后区域构造运动有明显增强迹象。2016年门源6.4级地震就是在这些观测反映挤压应力增强的背景下发生的,但此次地震事件可能并未完全缓解区域的应力积累,后续强震危险性仍需进一步关注。

Observation data of 4-component borehole strainmeter at Menyuan station were analyzed from different frequency bands. The results show that,under the background of compression,sharp compressional anomalies,space-time evolution of solid tide factors and the phenomena of increases of high frequency anomalies in different frequency bands increased from the latter half of 2012. The co-borehole water level observation also displayed that the subsurface fluid spread outside the station area,and led to fall of water level under the compressive stress background.GPS profiles which cross the major faults in the study zone also indicated that tectonic movement is strengthened obviously from 2013. The 2016 Menyuan M_S6.4 earthquake happened under the enhancing compression background reflected by the observations mentioned above. As the results indicated,the Menyuan earthquake had limited effects and probably didn＇t relieve the accumulated stress totally,the subsequent risk of strong earthquakes in the area needs more attention.