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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/67494


    Title: 三維結構中有限地震源模型之高效率波形反演;Efficient waveform inversions for finite-source models of moderate and large earthquakes in three-dimensional structures
    Authors: 謝銘哲;Hsieh,Ming-Che
    Contributors: 地球科學學系
    Keywords: 地震學;震波模擬;波形反演;有限震源模型;Seismology;Waveform simulation;Waveform Inversion;Finite-source Model
    Date: 2015-06-24
    Issue Date: 2015-07-30 19:43:16 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 一套快速而準確的地震有限震源破裂過程解算系統能有助於我們對地震發生前後之相關風險與災害的評估,實屬快速報告、防震減災之重要一環。此外,隨著對三維地下構造與地表地形的了解,將這些物理因素納入震波傳遞模擬、計算格林函數等工作,能更準確地評估地面運動。本論文將近年發表之台灣三維速度模型以及地表高程數據納入考量,發展出一套三階段之快速震源破裂解算系統,嘗試求解不同規模地震之有限震源破裂模型。該三階段包含:(1) 接獲地震速報後,快速搜尋點震源深度、震矩規模與震源機制;(2) 由震源機制判斷可能之破裂面與其平均破裂形式;(3) 由第二步驟所判斷之破裂面作為斷層面,反演中大規模地震之震源錯動量時空分佈模型。經一系列發生於台灣南、東部的中規模地震驗證,並與餘震、背景地震活動及前人研究結果等資訊比對,本論文所提供之方法能有效並快速地求解地震破裂過程。本論文亦應用前述方法,求解台灣中部南投地區一系列中規模地震(MW≈6)並提供構造解釋。該群地震有著相似的震源機制,卻有相當不同的深度。藉由本論文前述發展之方法,結果顯示深度小於20公里的地震,其破裂面為低角度朝東傾斜之斷層面,而深度大於20公里的地震,破裂面則為高角度朝西傾斜的斷層面,同背景地震活動與前人相關研究比對,本論文之結果為台灣中部共軛斷層面的存在及其形態提供了直接的地震學證據。為求更精確之地震源錯動量分佈,本論文亦採三維格林函數進行反演,並與一維格林函數反演結果比較,同時,反演過程亦考慮三維與一維之剛性係數分佈。通過研究發生於2013年10月31日之瑞穗地震,結果顯示三維模型能有效降低波形擬合殘差,並得到相對集中的錯動量空間分佈。通過上述研究分析與實踐,本論文所提供之快速反演地震破裂過程方法,可於個人甚至筆記本電腦、近自動化地求解地震源破裂過程,為地震減災、危險評估以及震源研究提供良好的參考資訊。
    ;For hazard mitigation and risk assessment, an efficient and well-designed algorithm to determine earthquake rupture properties in a short time is on demand. It is also important to account for effects of surface and subsurface structures to wave propagation and predict ground motion more accurately. In this thesis, we have developed an efficient three-step process which is used in solving for a finite-source model: A point-source focal mechanism is determined in the first step. Then, the two nodal planes in the point-source solution are used as trial candidates to solve for an average finite-rupture model and identify the actual fault plane. In the final step, a full slip distribution inversion is carried out based on the identified fault plane. We have adopted the source determination scheme to earthquakes near Nantou in central Taiwan for tectonic interpretations. We solved for the rupture properties of a series of moderate events (MW≈6), which show similar focal mechanisms but with different focal depths. Our determination on the rupture planes of these earthquakes suggest that the most of the shallow-focus ruptures occur on the low-angle plane, but on the high-angle plane for most of the deeper events, consistent with the background seismicity and support the existence of tectonically co-located active conjugate faulting system in central Taiwan. We also demonstrated the slip distribution inversion of a moderate earthquake in eastern Taiwan by our three-step procedure. Both broadband and strong motion stations are included in the inversion. Our results show that three-dimensional velocity model could provide better waveform fittings than one-dimensional model, and slip distribution is much more concentrated. Applications to moderate events (MW≈6) in southeastern and eastern Taiwan show that our source inversion technique is effective for semi-automatic, near real-time determinations of finite-source parameters for seismic hazard mitigation purposes.
    Appears in Collections:[地球物理研究所] 博碩士論文

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