Abstract：Using waveform data from Yunnan regional digital station network, we analyze the spatio-temporary variations of wave velocity ratio before and after MS≥ 5.5 earthquakes in western Yunnan and southwest Yunnan since 2011. Using the Wadati method of single station and multi-earthquake, we undertake dynamic tracking analysis on the variation characteristics of wave velocity versus time course curves of various stations within 160 km before the earthquakes, The results show that before the five earthquakes, there were low value anomalies, high value anomalies, low value-high value-low value anomalies, high value-normal medium-term anomalies, accounting for 56%, 33%, 16% and 15% respectively, and low value-high value returns, high value persistence, and low value persistence three short-term and imminent anomalies, accounting for 41%, 31% and 28% respectively. Comparative analysis of wave velocity ratio anomalies in different directions in the earthquake area show that before the two Yingjiang earthquakes, the obvious anomaly area is located in the southeast of the earthquake source, the prominent anomaly area before the Eryuan earthquake is located in the northeast of the earthquake source, and the obvious anomaly area before the Jinggu earthquake is located in Lincang area in the northwest of the Lancang river fault.
HE Yingwen,YANG Xiaolin,WANG Jianfang et al. Temporary Variation of vP/vS at Single Seismic Station before Recent Moderate and Strong Earthquakes in West to Southwest Yunnan[J]. jgg, 2019, 39(8): 798-803.