青藏高原雅鲁藏布江和班公湖-怒江缝合带附近深部结构研究

There are two core research to complete the application plan, one is to develop a set of perfect receive function prestack migration method, and the other is to obtain crust deep structure with high resolution beneath YZS and BNS applying the new method to process the wideband temporary seismic nets data deployed on Tibetan Plateau..The receiver function prestack migration method is able to obtain high resolution results based on the 2D velocity results from H-K method and transform function waveform inversion method and taking advantage of migration technology in seismic prospecting and scatter wave information. Especially, that can highlight the Moho offset or distinguish breakpoints from subsurface, so it overcomes these defects that traditional stack imaging method has a smooth interface and is difficult to identify offset..Plenty of temporary observation nets data on Tibetan Plateau(INDEPTH Ⅰ-Ⅲ, HI-CLIMB, ANTILOPE I-II and others) provides data guarantee for clear understanding deep structure beneath YZS, BNS suture zone. The application of the new method for further recognize deep structure provides technical support, especially to estimate whether existing Moho offset, which can provide important basis for the uplift of Tibetan Plateau process and dynamics mechanism.

申请计划完成两方面的核心研究，一是发展一套完善的接收函数叠前偏移方法，二是将其应用到青藏高原宽频带流动探测数据中，以期获得高分辨率的YZS、BNS缝合带的深部结构。.基于H-K方法、转换函数波形反演等方法获得的精细二维速度结构模型，借鉴地震勘探中的叠前偏移技术，同时有效利用地震散射波的信息，应用此接收函数叠前偏移方法能够获得高分辨的偏移图像。特别是能够突出象Moho面错断等奇点处的分辨，有效克服传统叠加方法成像结果较光滑而不易识别错断的缺陷。.青藏高原大量的流动观测数据（INDEPTHⅠ-Ⅲ、HI-CLIMB、Antilope I-II等）为清晰认识YZS、BNS缝合带的深部结构提供了数据保障。新方法的应用为进一步认清深部结构提供了技术支持，特别是认清缝合带是否错断了Moho面，能够为青藏高原的隆升过程及动力学机制提供重要依据。

在研究区域内搜集了Hi-CLIMB、INDEPTH -Ⅲ 临时台网数据、青藏高原研究所布设的ANTILOPE-Ⅰ、ANTILOPE-Ⅱ宽频带流动台网数据，进行了速度结构反演与偏移成像，获得了研究区域内地壳内速度结构及莫霍面形态特征等信息。在YZS缝合带附近莫霍面存在错断、断距达10km，即上隆分层结构，在BNS附近，莫霍面存在间断；地壳厚度由南向北逐渐加厚，在拉萨地体内最厚，在羌塘地体向北逐渐减薄；地壳内出现速度反转，存在局部低速体现象；地壳内东西向差异性小。推导了接收函数显式、隐式弹性各向同性2-D介质条件下正演公式，采用PML吸收边界，进行了接收函数正演模拟，为后续接收函数2-D非线性波形反演提供了研究基础。