青藏高原东北缘深地震测深震相研究与地壳细结构

通过对青藏高原东北缘不同构造单元深地震测深资料震相的综合分析，利用反射率理论地震图方法对实际记录模拟计算，进一步研究东北缘区域内部不同构造单元地壳细结构.结果显示：西秦岭褶皱造山带分隔了南北不同性质的地壳结构，北侧为相对稳定的临夏—兰州新生代盆地、南侧为强烈改造的松潘—甘孜地块；松潘—甘孜地块在青藏高原东北缘的构造演化过程中改造为萎缩的若尔盖高原盆地和盆地边缘褶皱造山两类不同的地壳结构；青藏高原东北缘中下地壳普遍存在以多层高低速相间、低速度结构为主的破碎松弛结构，这种特征在缝合带和造山带尤为明显，显示为地壳形变增厚、流变滑动的重要场所；结合二维速度结构及GPS研究结果，对青藏高原东北缘地壳形变及动力学过程进行了讨论.

Study on the crust phases of deep seismic sounding experiments and fine crust structures in the northeast margin of Tibetan plateau

In this paper the fine crust structures of the different tectonic units in the northeastern margin of Tibetan plateau are investigated in detail by means of comprehensive analyses of the crust phases on the recording sections of deep seismic sounding experiments in this region and comparing the observed seismic recording sections with the synthetic seismograms computed by the reflectivity method. The results reveal that the crust structures in the northern and southern parts of this region separated by the western Qinlin fold zone are quite different, and the crust structures are characterized respectively by stable Linxia-Lanzhou Cenozoic basin in the northern part and by strongly rebuilt Songpan-Garze tectonic block in the southern part. The results also show that Songpan-Ganzi tectonic block was rebuilt into two types of crust structures, i.e. the type of the shrunken Zoigê upland basin and the type of the folded orogenic zone in the basin margin. It is also revealed that fractured and relaxed structures widely exist in the middle and lower crust in the northeastern margin of Tibetan plateau, which are characterized by alternative low and high velocity structures or low velocity distributions. This structural feature appears especially obvious in the suture zone and the orogenic zone, which implies there are important places of thickening of the crust and rheological slip motion. The crust deformation and geodynamic process are discussed based on the 2D velocity structure of the crust and GPS result obtained in this region.