云南扬子准地台区地壳浅部速度构造特征  

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

作　　者：胡鸿翔[1] 冯永革[2] 

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]北京大学地球物理系,北京100871

出　　处：《西北地震学报》1998年第4期12-17,共6页Northwestern Seismological Journal

基　　金：国家自然科学基金资助课题;批准号:49574221.

摘　　要：描述了云南扬子准地台区洱源—江川深地震测深剖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10 km 以上,并且中新生代沉积也比别处厚.此凹陷区对应攀西古裂谷的南段,此处地震活动与岩浆侵入活动相对剖面的两端弱.剖面西段基底面起伏剧烈,在洱海地区形成小盆地.此处基底层内存在上隆的高速带,并对应有剧烈而又频繁的地震活动和基性岩浆岩活动.同样情况也存在于剖面的东段.说明地震活动性及岩浆活动与基底层内高速物质的分布存在对应关系.该高速物质估计为基性或超基性岩浆岩带,它是上地幔内半熔融岩浆物上涌的产物,它的活动触发了本地区众多地震.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 corre- sponding 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 corre- sponding relations between seismicity,magmatic activities and distribution of high velocity matters.These high velocity matters are estimated to be some basic or ultrabasic magmatic materi- als.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.

关 键 词：云南 波速构造 杨子构造区 地震活动性 岩浆活动 

分 类 号：P315.5[天文地球—地震学] P315.2[天文地球—固体地球物理学]