2010-08-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/705579摘要：西藏是由印度及歐亞兩板塊碰撞擠壓而逐漸形成的全球最高、面積最大的高原，也 因此成為學者們研究大陸板塊碰撞演化的最佳實驗場。過去的文獻中已有眾多為解釋西藏 高原如何形成所提出的假說，主要可歸成三大類：1.西藏岩石圈均勻增厚造成對流剝蝕 （convective removal） ，2.印度板塊近乎水平地下插至西藏，3.印度板塊（或歐亞板塊）高 角度隱沒至另一板塊之下。然而至今仍無定論。由於地震的 P 波及 S 波速與地球物質的溫 度及組成密切相關，西藏下方的速度分佈對此問題可提供許多關鍵的資訊。除此之外，大 陸板塊的碰撞牽涉到岩石圈的地殼及地函兩個部份，二者環環相扣。從構造動力學來看， 其下更深處的地函（包括軟流圈）的特性亦扮演著重要的角色。有鑑於此，本計畫將對西 藏地區的速度構造作一全盤仔細的研究，深度範圍涵蓋地表至地函過渡帶 （mantle transition zone） 約 700 公里處。對於地殼及淺部地函的速度剖面，將以目前廣泛應用的接收函數 （receiver functions）為基礎，並加上表面波資料一起逆推。較深層的構造則使用地震波多 重路徑（seismic triplication）的波形模擬來解，此方法過去較常用於地函過渡帶的研究，本 計畫中我將會把它延伸到岩石圈及軟流圈的交界。在過去十年間，西藏地區的地震觀測站 如雨後春筍般的不斷增加，不只整體地震網的孔鏡倍增，地震資料的品質也大幅提升，有 助於本計畫的進行。計畫結果將可幫助我們了解西藏下方的速度變化並作為西藏碰撞帶岩 石圈演化解釋上的依據。 <br> Abstract: Tibet, the world’s largest and highest plateau created by collisions between Eurasia and India, is the best site to understand how the continents respond to collision in large scale. Various models were proposed to explain the development of Tibet. The key end members include convective removal of homogeneously over thickened Tibetan lithosphere, horizontal underthrusting of the Indian lithosphere, or steep subduction of either plate. Seismic P and S velocities that can be linked to temperature and compositions of the Earth’s material are key constraints for resolving this issue. More over, the continental collision involves not only the crust of the lithosphere but also the mantle beneath. Both of them play important roles in the tectonic processes and link with each other. Therefore, in this study I propose to thoroughly investigate the velocity variations of Tibet from the surface to the mantle transition zone using two different approaches – 1) receiver function inversion and 2) modeling of waveform triplications. The former is widely used to constrain the crustal structure, and can be improved by including surface wave data. The latter is extended from my previous transition zone study but now the focuses are on the lithoephere-asthenosphere boundary. Owing to the large increase of modern seismometers recently deployed in Tibet, the data coverage and quality were greatly improved which makes the proposal a promising project. The goal is to resolve the current configuration of Tibetan lithosphere and understand how collision modifies the continental crust.西藏高原陸陸碰撞地震波多重路徑接收函數地函過渡帶Tibetan plateaucontinental collisionseismic triplicationreceiver functionsmantle transition zone