Abstract:To analyze the temporal and spatial evolution characteristics of wave velocity ratio before and after the January 2, 2022 Ninglang MS5.5 earthquake, we use the Wadati method of single station and multi-earthquake, and calculate the phase arrival time data of earthquakes that meet the calculation conditions recorded by Yunnan digital seismic network from January 1, 2020 to January 10, 2022. We analyze the wave velocity ratios of 59 stations of Yunnan and the wave velocity ratio of post-earthquake sequence recorded by the LGH and NLA stations closest to the epicenter. The results show that: 1)Ninglang earthquake occurred in the area with high wave velocity ratio in northwest Yunnan, and the high value area of wave velocity ratio is tending to expand with time. It may be that in the process of earthquake preparation, there is fluid infiltration in the cracks near the epicenter to reach the state of water saturation, resulting in the increase of wave velocity ratio. 2)The wave velocity ratios of the 4 stations within 100 km of the epicenter show the evolutionary process of continuous descent and earthquake, the time of wave velocity ratio begins to decline at the LGH station closest to the epicenter later than that of the other three stations. The preliminary analysis shows that the occurrence time of wave velocity ratio is negatively correlated with the epicentral distance. 3)There is better correspondence between the wave velocity ratio change of post-earthquake sequence and the activity of aftershocks, the wave velocity ratio sudden drops before the largest aftershock. When the earthquake sequence shows normal attenuation trend, the wave velocity ratio maintains stable low value.
ZHANG Tianyu,WANG Guangming,LIU Zifeng et al. Characteristics of Wave Velocity Ratio before and after Yunnan Ninglang MS5.5 Earthquake in 2022[J]. jgg, 2022, 42(11): 1156-1160.