研究生: |
陳耀傑 Chen, Yao-Chieh |
---|---|
論文名稱: |
利用台灣東部重複地震推估斷層滑移速率 Fault Slip Rate Inferred from Repeating Earthquakes in Eastern Taiwan |
指導教授: |
陳卉瑄
Chen, Hui-Hsuan |
學位類別: |
碩士 Master |
系所名稱: |
地球科學系 Department of Earth Sciences |
論文出版年: | 2017 |
畢業學年度: | 105 |
語文別: | 中文 |
論文頁數: | 89 |
中文關鍵詞: | 重複地震 、東部縱谷斷層 、深部滑移速率 、週期性波動 、成功地震 |
英文關鍵詞: | repeating earthquake, LVF, deep slip rate, periodic pulsing, Chengkung earthquake |
DOI URL: | https://doi.org/10.6345/NTNU202202821 |
論文種類: | 學術論文 |
相關次數: | 點閱:125 下載:10 |
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本研究首先以張育群(2013)所提出之台灣重複地震自動化偵測系統,建立全 台灣 2000 至 2011 年底規模 2 以上相似地震目錄,再進一步活動性最高的東部縱谷 斷層區域,建立生命週期大於 3 年之東部重複地震目錄,共 405 個序列。縱谷區域 重複地震在最南段集中於台東一帶共有 6 個序列,深度分佈為 5~30 公里;池上地 區共有 94 個序列、深度分佈為 4~30 公里;在玉里一帶,僅有 16 個重複地震序列 分佈,並於深度上呈現近乎垂直之分佈,深度集中於 8~20 公里;而北至花蓮一帶 呈現兩群東北–西南走向的重複地震群,分別發生在海岸山脈和中央山脈東翼下方, 總共有 184 個序列、深度在 5~37 公里。
根據其週期性之不同,利用復發週期之變異係數(coefficient of variance, COV) 0.3 為門檻值,將序列分為準週期性(Q-type, COV < 0.3)以及非週期性(A-type, COV > 0.3)序列,再根據非週期性序列對於大地震之反應不同,再細分為:受影響序列 (I-type,於鄰近大地震之後復發週期減少),以及新序列(N-type,該序列中第一 個事件發生於成功地震以後)兩種;並發現該兩種序列皆受 2003 年 12 月 10 日成功 地震影響,並僅分佈於池上一代,隨後利用前人之經驗公式推算各種序列之正規化 滑移速率後,發現準週期性序列之平均滑移速率於主震前後近乎一致,而其餘兩種 序列分別受到不同程度的影響。
除時間特徵外,以重複地震序列於空間上集中程度,可細部分區為花蓮東側 (HE)、西側(HW);池上北段(CN)、中段(CM)、以及南段(CS),利用移動 視窗平均計算區域滑移速率,我們發現 CN 以及 CM 皆受成功地震影響,於震後滑 移速率上升,震前的滑移速率分別為 1.4 和 2.09 cm/yr。不受大地震影響的 HE、HW 和 CS 其深部滑移速率則分別為 3.13、5.63 和 1.29 cm/yr。將這些數值和大地測量資 料所推估之斷層滑移速率相比,我們發現:池上地區重複地震集中於北段,並且深 部滑移速率與地表變形速率相比具有約 1 cm/yr 之盈虧,顯示可能於南段或較淺部 鎖定;玉里地區具有高深部滑移速率(4.96 cm/yr ),且重複地震分佈集中,可能於 某處具有無震滑移;花蓮東側和地表觀測結果相似,然西側位於中央山脈底下,其 高滑移速率亦高達 4.96 cm/yr,然無地表資料可供比對分析,其孕震機制及位置仍 尚待討論。
Creeping crustal faults often generate streaks of microearthquakes, but less commonly, they may still produce large earthquakes that rupture the brittle crust. The 150-km-long Longitudinal Valley Fault (LVF) in eastern Taiwan, characterized by ~ 1-3 cm/yr surface slip rate, is one of the best examples in the world that possesses earthquake potential in creeping segments. Built on the 2000-2011 earthquake catalog, we identified 405 M > 2 repeating earthquake sequences (RES) along the LVF and studied the recurrence property of the repeating earthquakes. The population of RES and the inferred deep slip rate revealed that: (1) the southern Chihshang area is locked in the southern half and creeping in the north with a deep slip rate of 1.4-1.5cm/yr at the depth of 10-25 km. The deep slip rate in southern half of the Chihshang fault was accelerated by the 2003 M6 ChengKung earthquake from inter-seismic rate of 1.92 cm/yr to 4.94 cm/yr; (2) the Yuli segment in the middle of the LVF is mainly locked but partially creeping in a narrow area with deep slip rate of 4.96 cm/yr at the depth of 10-20 km; (3) the Hualien segment reveals two fault strands, one beneath the coastline (likely the Meilun fault) that is characterized by ~2 cm/yr deep slip rate (similar to surface slip rate), the other underneath the Central Range with ~80 km spatial extent in the mapview and its deep slip rate of 4.96 cm/yr indicate a significant fast-slip fault motion that has been long neglected.
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