以TAIGER資料推求北部之速度構造; Modeling the Northern Taiwan Velocity Structure Using TAIGER Data

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Title:	以TAIGER資料推求北部之速度構造;Modeling the Northern Taiwan Velocity Structure Using TAIGER Data
Authors:	李柏寬;Bo-Kuan Li
Contributors:	地球物理研究所
Keywords:	台灣大地動力學國際合作計畫;台灣北部;波線追跡;速度構造;Northern Taiwan;velocity structure;TAIGER;Ray-tracing
Date:	2011-07-21
Issue Date:	2012-01-05 14:12:12 (UTC+8)
Abstract:	台灣位處歐亞板塊與菲律賓海板塊碰撞的聚合邊界，是全世界快速抬升的造山帶之一，地下構造複雜。本區域的板塊碰撞形式由兩個隱沒系統所形成：東邊的琉球隱沒系統及南邊的呂宋隱沒系統。本研究利用台灣大地動力學國際合作計畫(TAIGER)中的北部測線(T6)，藉由震測實驗所獲得的大量走時資料，嘗試在此區域建立一個完整的二維地殼速度構造剖面，同時描繪北台灣底下的莫荷面深度，探討台灣造山帶之碰撞模式。北部測線(T6)橫跨台灣北部，從新竹至宜蘭南澳間，總長約100公里，接收器間距為200公尺，共有5個主動式震源，炸藥量約750-3000公斤不等。同時，受限於東西向的測線長度不足，相較於淺層，深部的速度構造必須利用反射波來加以建構。本研究藉由大量走時資料，以波線追跡法對初達波及反射波相進行正推模擬，計算波線在速度模型中傳遞之理論走時，並比較理論走時和實際走時之差異，再對速度模型作修正，藉由反覆疊代，直至理論走時和實際走時擬合到達合理的程度。本研究初步研究結果如下：1）剖面整體速度由西向東呈現漸增的趨勢；2）西台灣底下可看出標準層狀構造；3）雪山山脈底下與中央山脈底下的側向速度有差異明顯，可推測兩者構造不同；4）淺層部分在主要地質分區以及構造線上皆有良好的對應，包括屈尺斷層與梨山斷層；5）莫荷面深度的分佈情形，同樣由西向東漸增，從西部平原的37公里，到中央山脈下最深約42公里，再往東則轉而變淺。 Taiwan is located at the converging boundary of Eurasian and Philippine Sea plates, which is one of the most rapidly uplifting orogeny in the world. The plate collision in this region involves two systems: the Ryukyu subduction system in the east and the Luzon subduction system in the south. In this study, we attempt to discover the velocity structure and the depth of Moho beneath Taiwan using the data collected by Taiwan Integrated Geodynamic Research(TAIGER) project, and to extend these results to improve the understanding of tectonic collisions in the Taiwan orogeny. In this study, we use the data from the E-W transect across the northern Taiwan (T6), and find the velocity structure by using first arrival times as well as reflection arrivals basing on the ray-tracing method. Forward ray-tracing is invoked iteratively to adjust the velocity variation until suitable fitting between observed and synthetic travel times are achieved. The preliminary results are: 1) the trend of overall velocity distribution along the profile increases from west to east; 2) a standard layered structure exists beneath the western Taiwan; 3) the lateral velocity variation is significant beneath Hsuehshan Range and Central Mountain Range, their structures are significantly different; 4) the shallow part of the velocity model corresponds well with the main geological structures and the boundaries along the Chuchih and Lishan faults are obvious; 5) the depth of Moho also increases from west to east, that is 37 km beneath the western plain, and about 42 kilometers beneath the Central Mountain Range, then turn shallower to further east .
Appears in Collections:	[Graduate Institute of Geophysics] Electronic Thesis & Dissertation

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