Crustal Structures of P-Wave and S-Wave Velocity off Taiwan and Philippine Sea Based on OBS Data (II)

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Project title

Code/計畫編號

MOST103-2611-M019-013

Translated Name/計畫中文名

臺灣及鄰近地區地體動力學研究－子計畫：臺灣與菲律賓海之海底地震儀震測地殼P 波與S 波速度構造研究 (II)

Project Coordinator/計畫主持人

Tan-Kin Wang

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=8357907

Year

2014

Start date/計畫起

01-08-2014

Expected Completion/計畫迄

31-07-2015

Bugetid/研究經費

752千元

ResearchField/研究領域

海洋科學

"本年度將使用水平移位速度、同反射點訊號平化與殘餘速度頻譜分析跨越花東海盆、加瓜海脊、西菲律賓海盆、琉球海溝、耶雅瑪增積岩體、琉球弧前海盆以及琉球島弧的三條長支距反射震測剖面 (2009 年 TAIGER 航次 T4、T5 與 T6)，得到重合前深度移位速度模型。藉以觀察花東海盆、西菲律賓海盆及琉球弧前海盆沉積物基盤深度變化、花東縱谷與北呂宋島弧碰撞的構造變化、加瓜海脊北端隱沒至琉球海溝及耶雅瑪海脊下方之情況、琉球隱沒帶的逆衝斷層、基盤斷層、分支斷層與隱沒滑脫面。重合前深度移位技術不但可計算沉積層 P 波速度及建立深度移位震測剖面，也能轉換為海底地震儀震測沉積層 P 波速度模型。第二年將利用第一年水平速度分析及重合前深度移位震測剖面建立的沉積層 P 波速度構造，結合海底地震儀水壓及垂直分量資料進行走時反演，獲得到跨越花東海盆、加瓜海脊、西菲律賓海盆、琉球海溝、耶雅瑪增積岩體、琉球弧前海盆以及琉球島弧之地殼 P 波速度構造。本研究不但以折射初達波及首波訊號分析地殼速度變化，也使用反射波走時解析地殼構造界面。第三年則接續第二年成果，分析海底地震儀水平分量資料，建立花東海盆、加瓜海脊、西菲律賓海盆、琉球海溝、耶雅瑪增積岩體、琉球弧前海盆以及琉球島弧之地殼 S 波速度構造。從臺灣與菲律賓海之間地殼 P 波與 S 波速度構造，可探討菲律賓海地殼構造、琉球隱沒帶附近的地震與岩漿活動等。藉以探討板塊碰撞造成的斷層、岩漿與破裂帶分佈以及其孕震機制。""In the first year of the project, velocity models along 3 long-offset reflection profiles (TAIGER Lines of T4, T5 and T6 collected in 2009) across Huatung Basin, Gagua Ridge, West Philippine Basin, Ryukyu Trench, Yaeaema Accretionary Prism, Ryukyu Forearc Basins and Ryukyu Arc will be analyzed by horizontal velocity analysis, flattening of common-reflection points, residual velocity semblance and pre-stack depth migration (PSDM). Based on the PSDM models, sedimentary basement in the Ryukyu Forearc Basins, Huatung Basin and West Philippine Basin, subduction of Gagua Ridge beneath the Ryukyu Trench and the Yaeaema Ridge, thrust faults, basement faults and splay faults and decollement in the Ryukyu subduction zone can be found. PSDM can be used to calculate the P-wave velocities of the sediment and to build the depth migrated profiles that can be transformed as the P-wave velocity models of the sediment for ocean-bottom seismometer (OBS) data processing. In the second year, by integrating the sedimentary models imaged from PSDM, we will invert P-wave velocity models of the crustal structures across Huatung Basin, Gagua Ridge, West Philippine Basin, Ryukyu Trench, Yaeaema Accretionary Prism, Ryukyu Forearc Basins and Ryukyu Arc by travel-time arrivals picked from hydrophone and vertical components of OBS data. Our study will not only analyze P-wave velocity of the crust from the first arrivals and head waves, but will also use the reflected arrivals to constrain the crustal interfaces. In the third year, based on the results of the second year, crustal S-wave velocity models across Huatung Basin, Gagua Ridge, West Philippine Basin, Ryukyu Trench, Yaeaema Accretionary Prism, Ryukyu Forearc Basins and Ryukyu Arc can be built from horizontal components of OBS data. From crustal P-wave and S-wave velocity models between Taiwan and Philippine Sea in these studies, crustal structures in the Philippine Sea, earthquakes and magmatic activity in the Ryukyu subduction zone will be observed. Furthermore, the distribution of faults, magma, fracture zones and the seismogenic mechanisms, formed by collision between the Philippine Sea Plate and Eurasian Plate, will be evaluated by the integration of crustal P-wave and S-wave velocity structures between Taiwan and Philippine Sea."

Keyword(s)

加瓜海脊
北呂宋島弧
海底地震儀
琉球隱沒帶
Gagua Ridge
Northern Luzon Arc
Ocean-bottom seismometer
Ryukyu

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Crustal Structures of P-Wave and S-Wave Velocity off Taiwan and Philippine Sea Based on OBS Data (II)

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