南京及邻区数字地震波速比变化特征分析

Analysis of Variation Characteristics of Digital Seismic Wave Velocity Ratio in Nanjing and its Adjacent Area

利用2010年1月—2017年9月南京市及邻区数字化地震资料的P波和S波震相,采用单台多震和达法和单震多台和达法分别获得了各台站波速比随时间变化曲线以及南京地区波速比空间分布,结果表明:(1)南京及邻区波速比在1.6340~1.7007,各个台站出现最低值时间不同步;(2)南京区域6个地震台站波速比变化不同,六合、江宁和南京台波速比在地震发生前2年,波速比大幅度下降,然后在一段时间内保持在低值附近波动,波速比回升后,发生主震。浦口、溧水和高淳台在波速比下降区发生地震,变化趋势不明显;(3)波速比空间分布结果显示,2次地震前、后波速比空间分布的差异性明显,区域内的波速比值较均匀,高、低值的异常区显著。

Based on the P-wave and S-wave of digital seismic data from Jan. ,2010 to Sep. ,2017 in Nanjing and itsadjacent areas, we analyzed wave velocity ratio of each station with time and the spatial distribution of the wavevelocity ratio in Nanjing area by using Wadati method of single station and multi-earthquake and Wadati method ofsingle earthquake and multi-station. The results show that： （1） The wave velocity ratio was between 1.6340 and 1.7007 in Nanjing areas, the time of minimum wave velocity ratio at each station is not synchronized. （2） Thevariation of wave velocity ratio of 6 seismic stations in Nanjing area is different. The wave velocity ratio of Liuhe,Jiangning, and Nanjing Stations decreased in two years before the two earthquakes in Najing area in 2016, and thenkept fluctuating around low values for a period of time. After the wave velocity ratio rised again, the main shockoccurred. The earthquake also occurred at the area of decresing of wave velocity ratio of Pukou, Lishui and GaochunStations, and the variation of wave velocity ratio of other stations is not obvious. The results of the spatial velocitydistribution of the wave velocity ratio show that the spatial distribution of the wave velocity ratio before and after thetwo earthquakes in 2016 is obviously different. The wave velocity ratio in the study region is relatively uneven, andanomaly regions with the high and low values are significant.