Abstract: 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.

Key words: Borehole strain, Borehole water level, GPS, The 2016 Menyuan M_S6.4 earthquake