Research of Anomaly in Fix-Point Deformation Prior to Qinghai Menyuan MS6.4 Earthquake in 2016

Abstract

Based on the observation data of the fix-point deformation precursor in Gansu, Qinghai, Ningxia and Inner Mongolia, this study investigates the Qinghai Menyuan MS6.4 earthquake which occurred in January 21, 2016, and applied the S-transform temporal-frequency analysis method to calculate and extract the short-impending high-frequency anomalies in five stations prior to this earthquake: borehole strain of Menyuan station, borehole tilt of Huangyuan station, borehole title of Sitan station, borehole strain of Haiyuan station and borehole tilt of Liangshui station. On the basis of the interference elimination and the data quality assessment, the frequency spectral characteristics and temporal-spatial distribution characteristics of high-frequency anomalies prior to the earthquake are analyzed and studied. The study results indicate that prior to the Menyuan earthquake, on the basis of the background signals, massive signals with a period of about 10-60mins emerged in multiple stations. In addition, the spatial distributions of the signals conformed to the openness and nonlinearity characteristics of the deformation anomalies while the energy amplitude expanded as the earthquake approached, and then attenuated gradually subsequent to the earthquake. Concerning the temporal characteristics, as the epicentral distance became shorter, the occurrence and duration period of the anomalies gradually shortened, and the impending earthquake anomalies gradually increased. Besides, the anomalies migrated from the peripheral region to the source region. The study conclusions are of great significance to the temporal-spatial evolutionary characteristics of short-impending anomalies prior to strong earthquakes.