云南扬子准地台区地壳浅部速度构造特征

描述了云南扬子准地台洱源－江川深地震测深部面初至波的详细分析解释结果，所用方法为改进的射线追踪法。结果表明，在剖面中段沉积盖层巨厚，基底面下陷最深可达１０ｋｍ以上，并且中新生代沉积也比别处厚。

THE CHARACTERISTICS OF VELOCITY STRUCTURE IN SHALLOW PART OF THE CRUST IN YANGTZE PARAPLATFORM REGION OF YUNNAN PROVINCE

In this paper,the results of detailed interpretation on primary waves in the Eryuan-Jiangchuan deep seismic sounding profile in Yangtze paraplatform region of Yunnan Province are presented.Here the improved ray-trace method is used.The results show that in the middle part of the profile there is very thick sedimental cover.The basement interface here is depressed and its depth is more than 10 km.The Meso-Cenozoic sediment thickness is also greater than other places.This depressed region is corresponding to southern part of ancient Panxi rift valley.In this place the seismicity and magmatic intrusion are relatively weaker than other two ends of profile.In its western part the basement relief is quite changeable and a small basin formed in the Erhai lake region.In the basement layer there exist raised places with higher velocity and there are corresponding violent frequent seismicity and basic magmatic intrusion.The similar situation also takes place in eastern part of the profile.It means that in the basement layer there exist some corresponding relations between seismicity,magmatic activities and distribution of high velocity matters.These high velocity matters are estimated to be some basic or ultrabasic magmatic materials.They are the products of semimelting magmatic matter upwelling from deep upper mantle. Their activities trigger occurrences of a lot of earthquakes in the region.