以數值模擬討論南段中央山脈正斷層發育;Numerical Simulation on the Normal Fault Development in Southern Central Range

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Title:	以數值模擬討論南段中央山脈正斷層發育;Numerical Simulation on the Normal Fault Development in Southern Central Range
Authors:	沈怡君;Shen, Yi-Jiun
Contributors:	地球科學學系
Keywords:	南段中央山脈;正斷層;三維數值模擬;恆春半島造山
Date:	2022-07-25
Issue Date:	2022-10-04 11:11:49 (UTC+8)
Publisher:	國立中央大學
Abstract:	臺灣島位在菲律賓海板塊與歐亞板塊兩板塊之間，中央山脈在兩板塊擠壓的地體環境下所形成。然而，長時間處在擠壓環境的中央山脈南段部分（23.5°N以南），在過去的BATS地震目錄中可以看到相當特殊的情況，在淺部（深度小於10公里）大致上的地震機制解皆為正斷層以及走向滑移斷層解，而不是以逆斷層為主的破裂型態。因此，本研究利用數值模擬方式做三維地球動力求解，在簡化的模型設計下，探討中央山脈的地體構造如何發育，進而形成正斷層以及走向滑移斷層地震。在台灣南北造山時序的差異下，本研究區域的北方完成造山，而南方則尚未，故地層屬於較鬆軟的狀態，因此假設在此情況下中央山脈物質會向南方移動。本研究結果中驗證物質必須有南北向的流動才得以與現況吻合，一方面造成了正斷層地震，另一方面也是恆春半島造山的材料來源，從各項參數實驗中了解，中央山脈的深部物質密度須小於西部麓山帶下部地殼與海岸山脈的密度，以及盡量小於淺部中央山脈物質的密度，且結果與前人P波波速相關研究得以相互解釋，有助於了解中央山脈的地下物質特性。綜合上述，此區域的地體複雜度包含縱向、東西向以及南北向的因素，無法僅透過二維的模型就簡單說明，必須以三維的方式進行討論。 ;Taiwan Island is located between the Philippine Sea Plate and the Eurasian Plate. However, in the BATS earthquake catalog, an interesting thing we can find is that the focal mechanisms in the southern Central Range are normal faults and strike-slip faults, but not reverse faults. Therefore, our study uses the numerical simulation method to solve the three-dimensional geodynamics. Under the simplified model design, explore how the tectonic development of the southern Central Range forms normal faults earthquakes. Due to the difference in the orogeny sequence between the north and the south of Taiwan, the northern part of our study area has completed orogeny, but the southern part not yet. So, our study assumed that the material in the Central Range will flow to the south. The results verified that the material must have a north-south flow to be consistent with the current situation. On the one hand, the normal fault earthquake is caused, and on the other hand, it is also the source of the orogenic material of the Hengchun Peninsula. Other results show the density of ductile Central Range must be lower than the density of the lower crust in the Western Foothills and Coastal Range, as well as the density of brittle part as much as possible. To sum up the above, the complexity of the southern Central Range includes vertical, east-west, and north-south factors, which cannot be simply explained through a two-dimensional model, and must be discussed in a three-dimensional way.
Appears in Collections:	[Graduate Institute of Geophysics] Electronic Thesis & Dissertation

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