南琉球隱沒系統位於菲律賓海板塊（PSP）與歐亞板塊（EUP）交界，在過去的歷史上有大地震發生甚至引發海嘯，因此，瞭解此地區的地體構造是很重要的。在前人研究中，菲律賓海板塊隱沒的地球物理資料並不十分的多，對於菲律賓海板塊隱沒到歐亞板塊的詳細的地體形貌仍未完全掌握，所以本研究利用高解析度的震測影像資料希望能提供更多的資訊。然而，海洋震測影像時常會受到複反射的影響而使深部地殼影像受到干擾。因此，為了得到板塊邊界及莫荷面反射的成像，本研究採用不同去除複反射方法提高深部地殼訊號。資料來源是2009年TAIGER計畫中在南琉球施測的多波道震測剖面(MGL0906_18N；MGL0906_15N；MGL0906_30A)，施測規劃為測線每50公尺一個炸點，受波器每12.5公尺一個，共深點(CDP)是6.25公尺，紀錄時間15秒。震源是低頻訊號(20Hz~60Hz)，能穿透淺層沉積物，反射深部的地殼訊號。因為複反射會影響深部構造的訊號，因此本研究利用震測軟體處理，使用各種方法去除或減弱複反射效應，提高莫霍面的訊號達到我們的研究目的，提供琉球海域高解析度的地球物理數據。本研究使用四種方式去除複反射。第一，利用消除海表面造成的複反射(SRME)；第二，利用Radon轉換減弱複反射；第三，預測解迴旋(Predictive Deconvolution)；第四，傾角濾波去除複反射。經過這些步驟，增積岩體和弧前盆地下方的地殼反射訊號清楚成像。此成效可被應用於其它琉球隱沒系統的震測剖面中，在未來可以更瞭解此地區隱沒的邊界狀況。

The southern Ryukyu subduction system is located at the boundary between the Philippine Sea Plate (PSP) and the Eurasian Plate (EUP). The Philippine Sea Plate subducts northwestward beneath the Eurasian Plate near the eastern offshore of the Taiwan orogen. The Ryukyu subduction system is potentially hazardous in terms of tsunami and ground shaking for Taiwan region. Therefore, it is important to understand the crustal structure of this subduction system. In previous studies, the geometry of the subducting PSP is not clear, so we want to process high-resolution crustal-scale seismic images. However, crustal reflections are usually covered by the multiples from sea floor. In order to imagine the plate boundary or even moho reflection, the advanced multiple attenuation methods need to be applied for studying the crustal deformation in the subduction zone. In this study, we applied the multiple attenuation methods to the multi-channel seismic profiles (MGL0906_18N；MGL0906_15N；MGL0906_30A) in the southern Ryukyu subduction system from TAIGER (Taiwan Integrated Geodynamic Research) project in 2009. The field experiment parameters are 50 m shot interval, 12.5 m spacing for the hydrophone, 15 s of recording time, and 6.25 m of CDP spacing. In those profiles, the top of subducting crust of the Philippine Sea Plate is hidden by the multiples. Due to multiples affect on the deep structure signals, we use several de-multiple methods to remove the multiple effects, and increase signals from deep crustal reflectors. In this study, four steps of multiple attenuation methods are used (1) 2D Surface Related Multiple Elimination (SRME), (2) Radon Transform multiple attenuation, (3) Predictive Deconvolution, (4) Dip filter. After these steps, the top of subducting plate below the accretionary prism and the east Nanao basin is clearly imaged. Those methods can be applied to other marine seismic profiles in the future.

中文摘要 i
英文摘要 ii
致謝 iii
目錄 iv
圖目錄 vi
表目錄 ix

第一章 緒論 1
1.1 研究動機與目的 1
1.2 研究區域概述 3
1.3 南琉球隱沒系統之地體構造 5
1.4 板塊構造活動 9
1.5 南琉球海域之地震特性 17
1.6 南琉球弧前基盤之型態 24
1.7 本文內容 27
第二章 消除複反射方法及原理 28
2.1 複反射的成因及類型 28
2.2 預測解迴旋(Predictive Deconvolution) 35
2.3 頻率-波數域濾波器(F-K filter；Frequency-wavenumber filter) 38
2.4 傾角濾波(Dip filter) 39
2.5 Slant-Stack Transform 41
2.6 Radon Transform 44
2.7 特徵向量濾波(Eigenvector filter；Karhunen-Loeve Transform) 48
2.8 波動方程式(WEMA；Wave Equation Multiple Attenuation) 49
2.9 SRME (Surface-Related Multiple Elimination) 51
第三章 震測資料收集及處理 54
3.1 海上震測資料收集 54
3.2 重合數計算 58
3.3 資料處理 59
3.3.1 資料讀取與展示 60
3.3.2 幾何定位（Geometry） 60
3.3.3 近支距炸點展示（Near-offset trace display） 60
3.3.4 初疊加（Brute-stack） 63
3.3.5 帶通濾波（Band-pass filter） 63
3.3.6 球面擴散修正（Spherical divergence correction） 63
3.3.7 速度分析（Velocity analysis） 69
3.3.8 垂直隔距時差修正（NMO, Normal moveout correction） 69
3.3.9 重合（Stack） 72
3.3.10 移位（Migration） 72
3.3.11 自動增益控制（AGC, Auto gain control） 72
3.4 消除複反射 73
3.4.1 預測解迴旋（Predictive Deconvolution） 73
3.4.2 頻率-波數域濾波器（F-K filter） 76
3.4.3 特徵向量濾波（Eigenvector filter） 79
3.4.4 傾角濾波（Dip filter） 81
3.4.5 Slant-Stack Transform 83
3.4.6 Radon Transform 87
3.4.7 波動方程式（Wave Equation Multiple Attenuation） 90
3.4.8 SRME（2D Surface-Related multiple elimination） 91
第四章 研究結果與討論 94
4.1 複反射衰減結果 94
4.1.1 比較各種方法去除複反射效果 94
4.1.2 探討各種方法處理成效 95
4.2 展示複反射消除流程 105
4.3 震測剖面解釋 113
第五章 結論 122
參考文獻 124

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