The Study for Slab Structure beneath Northern Taiwan (II)

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基本資料

Project title

Code/計畫編號

NSC97-2116-M019-005

Translated Name/計畫中文名

台灣北部地區隱沒構造研究(II)

Project Coordinator/計畫主持人

Yi-Ling Huang

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Institute of Earth Sciences

Website

https://www.grb.gov.tw/search/planDetail?id=1676817

Year

2008

Start date/計畫起

01-08-2008

Expected Completion/計畫迄

01-07-2009

Bugetid/研究經費

678千元

ResearchField/研究領域

地球科學

"台灣與鄰近區域的地體構造，關係複雜緊密相連。台灣東北部外海隱沒帶附近的地震顯示出當地地下複雜的變形作用，其不但缺少系統性的地震機制分佈，對於海溝、海脊等重要構造線亦無法明確顯現。此外，碰撞作用亦導致應變的轉移，利用地震活動的分佈也顯示出台灣東北部的菲律賓海板塊西部邊界比現今研究所認定的大致位置還要向西延伸至少150 公里。多年來各方研究對此區域提出了各種見解，直至目前仍有許多疑惑未有定論，更加顯現台灣北部地區地體構造的複雜性。藉由地震活動的空間分佈，我們雖可得知隱沒板塊大致的樣貌，然而地震的空間分佈反應出的是應變釋放的位置，這些位置不見得是板塊與周圍環境速度不連續的位置，故難以準確的描述隱沒板塊的上部邊界。除了利用地震的空間分佈，速度層析法也可提供隱沒板塊的大致樣貌，然此法也因提供的是平均的速度效應，無法直接反應隱沒板塊與周圍環境速度不連續的確切位置。當震波穿過速度不連續的界面時，P 波與S 波會相互轉換而形成轉型波，其能敏感反應介質速度的不連續，利用轉型波來描繪隱沒板塊的上部邊界位置是個不錯的方法。本計畫將針對菲律賓海板塊隱沒邊界問題加以探討，期能對隱沒板塊的上部邊界位置有更確切的了解。這些更進一步的了解除了對板塊邊緣地震定位的準確有直接性的幫助外，還能對速度構造及其相關研究提供助益，並可增進對隱沒板塊和上伏大陸板塊間的耦合機制及發生在逆衝區的大規模破壞性地震的了解，此對加強都會區的強震防災也有一定的助益。" "The tectonic structures in Taiwan and nearby region are complex: in northeastern Taiwan, the Philippine sea plate goes under the Eurasian plate along the Ryukyu arc; in southern Taiwan, the Eurasian plate subducts under the Philippine sea plate along the Manila trench; Taiwan is between these two subducting structures, which was formed of collision between Luzon arc and Eurasian plate. The seismisity in northeast region of Taiwan shows a completely complex deformation and the collision in this area causes the shift of strain. Moreover, the seismic mechanisms are not systematic and can’t display trenches and ridges. The temporal and special distribution of earthquakes shows us the rough shape of a subducting plate, but the shape doesn’t figure the exact position of velocity discontinuity. Tomography provides an average velocity image and figures the subducting structure, but it also can’t indicate the exact position of velocity discontinuity. P waves and S waves can convert into each other when they travel through a discontinuous velocity structure. They are so-called converted waves and sensitively reflect they travelled through a discontinuity. It is a good choice to use converted waves to study subducting structure. Many studies about subducting structure in northern Taiwan and their results have been published, but there are also many questions have no answers. The aim of this research is using converted waves to study the slab structure and try to figure the exact upper boundary of subduction zone. The results of this research will improve not only earthquake locating, but also help us to understand the coupling mechanism of two collision plates and the large earthquakes in trust zone."

Keyword(s)

隱沒構造
轉型波
速度構造
slab structure
converted waves
discontinuity

DSpace CRIS

The Study for Slab Structure beneath Northern Taiwan (II)

基本資料

Description