【摘要】 对华东三个活动地块区进行了波速比时空对比分析,发现:各活动块区的波速比曲线随时间变化形态差异较大,目前仅鲁东黄海块体处于波速低值异常,但是异常幅度比较小,短期内发生中强地震的可能性不大;空间分布上主要以低值异常为主,近三年的波速比低值异常主要集中在山东南部地区。同时结合安庆MS4.8、高邮MS4.9等震例,在震前高值区会明显出现大范围离散-收敛(发震)-离散现象。更多还原

【Abstract】 Zhang Guomin et al.(2005)presented the Chinese active block division research results,analyzing the regional characteristics of East China seismic geology and seismic activity on three plots.(Comparing seismic wave velocity space and time,we can see that each earthquake block’s seismic wave velocity curve changes with time differences.In the eastern part of Shandong Province and in the Yellow Sea seismic block,recent seismic velocity shows low-value anomalies,but the abnormal amplitude is relatively small,and therefore the possibility of moderately strong earthquakes occurring in the short term is small.East China seismic wave velocity distribution in space is connected to low-value anomalies;in nearly three years of seismic wave velocity spatial distribution,East China Earthquake low velocity ratio anomalies were mainly concentrated in southern Shandong Province.Analyzing this together with the Anqing MS4.8and Gaoyou MS4.9earthquake characteristics,a high-value area before an earthquake will show a significantly large scope of discrete convergence phenomena.The East China area,which spans the three tectonic units North China,Southern China,and Yellow Sea,has a complex geologic structure.The regional deep fault has an obvious effect on the regional tectonic movement and strong earthquake activity and distribution.The Tancheng-Lu-jiang(Tan-Lu)fault zone,agreat fault across the East China area,spawned the Jiangxi region’s2005Jiujiang-Ruichang MS5.7earthquake,as well as the Dingyuan MS4.2,Anqing MS4.8,Ruichang-Yangxin MS4.9,and Gaoyou MS4.6earthquakes.In this fault belt,the intensity and frequency of moderate seismic activity is significantly increased.Studying the East China region,especially the ratio of wave velocity features near the area of the Tan-Lu fault zone,can give a scientific basis for the seismic trend in the region,enhance the use value of seismic station information,and realize the organic combination of earthquake monitoring and prediction.This study uses the China Earthquake Networks Center earthquake catalog data for the East China area(27°~38°latitude,111°~125°longitude)to calculate that,for a Richter magnitude where ML≥1,there were 2 815 events from January 2008 to September 2013,with a seismic wave velocity ratio of 1834.According to the East China region’s boundary and tectonic characteristics,the study area is divided into the North China,Southern China,and the Eastern-Yellow Sea blocks(Figure 1)to study and analyze the data.As Figure 1shows,the distribution of earthquakes is relatively uniform,and the area of earthquake monitoring station density is high,so that the spatial and temporal characteristics of wave velocity ratio representing the region calculate the wave velocity ratio very well.更多还原