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標題: | 熱液換質與地溫梯度控制菲律賓斷層於萊特島北段與中段之潛移行為 Hydrothermal alternation and geothermal gradient control the creeping behavior of the Philippine fault on the Leyte segment |
作者: | Wei-Ching Hung 洪煒晴 |
指導教授: | 胡植慶(Jyr-Ching Hu) |
關鍵字: | 菲律賓斷層,萊特島,潛移,持久散射體雷達干涉技術,小基線時間序列分析,震間滑移,鎖定深度, Philippine Fault,Leyte Island,Creeping,PS-InSAR,Small Baseline Subset Time Series Analysis,Interseismic Slip Rate,Locking Depth, |
出版年 : | 2019 |
學位: | 碩士 |
摘要: | 菲律賓位於歐亞板塊與菲律賓海板塊的聚合帶上,其中菲律賓斷層與一系列隱没作用的斷層系統最為活躍。菲律賓斷層長約1200公里,為一左移走向滑移斷層,形成原因為兩板塊間的斜聚合而形成滑移分配。前人GPS研究顯示該斷層的萊特島段有潛移現象每年約25-30 mm/yr。2017年7月6日發生了一個規模6.5的大地震,且地表破裂位置剛好與前人研究所認定的主要潛移區域吻合,因此研究該斷層的潛移特性與原因在地震災害評估領域上具有重要的意義。本研究主要是使用永久性散射體差分干涉法(PS-InSAR),利用2007-2011年的ALOS PALSAR L-band衛星影像進行小基線時間序列分析菲律賓斷層於萊特島中部至北部之潛移活動特性,並藉由數值模擬,了解菲律賓斷層萊特島段的潛移分布、能量累積與釋放機制。由PS-INSAR升軌道之橫跨斷層視衛星方向(LOS)速度場資料顯示,於萊特島中段、北段跨過斷層有很大的速度變化,指出了該地區於間震期的變形行為趨向潛移,橫跨斷層的速度場變化約為10-16 mm/yr;而萊特島南段跨斷層之速率變化趨近於零,故判定為鎖定區段。前人研究推測該地的潛移現象和萊特島中部與北部有大量的第四紀火山有關,高地溫梯度使得斷層較易發生潛移行為。我們另外比對了該地的大地電磁電阻測量資料,發現低電阻的區域和我們PS-InSAR處理結果中,橫跨斷層有高速度場變化的地方高度重疊。我們認為這和該處受高度熱液變質作用而產生的蒙脫石至伊來石等片狀礦物有關,片狀礦物造成速度強化效應,導致斷層弱化,使其更易發生潛移現象。 The Philippine Fault is a 1,200 km long sinistral strike-slip fault that is resultant from the slip partitioning of the oblique convergence between the Philippine Sea Plate and Eurasia Plate. Aseismic creep with a rate of ~25-30 mm/yr along the Philippine fault on Leyte island has been inferred from campaign GPS analysis. However, an Mw 6.5 earthquake event occurred on 6 July 2017 and ruptured the creeping segment on the Leyte near the Tongonan geothermal field, which is a crucial topic to characterize the along-strike and down-dip spatial distribution of seismic and aseismic creeping segments. In this study, we use Small Baseline Subset (SBAS) time series analysis approach and numerical modeling to estimate the interseismic slip rate across the Philippine fault on Leyte island with 2007-2011 ALOS-1 PALSAR ascending and descending data. The LOS mean velocity field clearly shows discontinuity across the fault, which is evidence for shallow fault creeping. The discontinuity of LOS velocity across the fault at the northernmost and the middle part of Leyte is about 10-16 mm/yr based on ascending data. However, this phenomenon does not happen in the southern part of Leyte Island, this might indicate that the creeping phenomenon varies along the fault. We are carrying out the numerical modeling based on the mean LOS velocity fields to characterize the locking depth and slip deficit rate along the Philippine fault on Leyte island. Previous study suggested that the creeping behavior could be controlled by the high geothermal gradient in the Togonan geothermal filed and active volcano on the north most of Leyte island supported by the coseismic slip deficit of the 2017 Mw 6.5 event. Alternatively, the creeping behavior could be also controlled by the velocity-strengthening behavior of the clay minerals in the hydrothermal alteration in the geothermal field. We found high consistency of the areas with the discontinuity of LOS velocity across the fault in PS-InSAR analysis and areas with low magnetotelluric resistivity. Thus, we infer that this may be related to the hydrothermal alteration of volcanic activity, which leads to weaken the fault and cause the creep phenomenon. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/73829 |
DOI: | 10.6342/NTU201903674 |
全文授權: | 有償授權 |
顯示於系所單位: | 地質科學系 |
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