臺灣博碩士論文加值系統

　　台灣為地震活動頻繁的區域，而地震與構造之活動息息相關。然而地震震源的深度，常常超過傳統地質調查及地球物理探勘如震測剖面及鑽井所能提供的資料深度。因此解析地震震源分布為瞭解地下構造的型態提供了另一個方向。
　　本研究利用震源位置疊合法調整1998年規模6.2瑞里地震的主震及餘震震源位置，使地震的分布構造較清楚的顯示出來。利用三維模型處理軟體GOCAD的輔助，建立地震分布構造模型。另一方面，依據已發表的地質資料，於GOCAD中重建造成瑞里地震之大尖山斷層的地下斷層構造模型。依此而探討1998年瑞里地震之主餘震與大尖山斷層及其他地質構造之間的關係。
　　地震模型顯示，瑞里地震的餘震分布呈現出一個“ㄟ”字型的曲面。可將其分為兩個構造面：一為淺而平緩的面，深度約6-7km，以小於10度的傾角向東傾斜；另一為西北─東南走向，以60-70度向東北傾斜的陡峭面，深度為6-10km。主震之位置即位於兩個面相接轉折之處。地下斷層模型顯示，大尖山斷層可分為三個主要的構造面：（1）主要斷層斷斜面（Main Ramp），北北東走向，傾角30度向東，深度由地表至6公里；（2）側向滑移面（Lateral Ramp），北西走向，傾角30-50度向東北；（3）主要斷平（Flat）或基底滑移面（Decollément），走向為南北向，傾角6度向東，深度自六公里往下延伸。而瑞里地震之主震位置落於側向滑移面轉為基底滑移面處。依據發震構造模型與地下斷層構造模型的空間分布與幾何型態，此“ㄟ”字型曲面之發震構造可視為大尖山斷層的縱向與側向延伸構造。由主震震源機制解顯示，瑞里地震之主要破裂面可能發生在大尖山斷層的側向滑移面上，並可能延伸至主要之斷層面上。
　　本研究由地震震源分布成功的建立了地震構造模型，此方法可應用在震測資料與地質資料還無法解釋的深度，從而重建地下深部的構造。配合地質構造模型，可較完整的呈現地體構造的型態，對於了解斷層與地震的性質，提供我們更多的線索。

Earthquakes are related to active tectonics. The earthquakes are distributed largely within the whole crust. Thus the level of the earthquakes is usually much deeper than that geological survey and geophysical investigations can reach. Therefore, the distribution of the seismicity provides a good opportunity for understanding the subsurface geological structures. Due to Plio-Pleistocene plate convergence and ongoing mountain building processes, numerous earthquakes frequently occur in the Taiwan region. For the purpose of reconstructing the subsurface structures, this study focuses on the comparison between the seismogenic structures (derived from the seismicity distributions and the focal mechanism) and the geologic structures (inferred from the surface and subsurface available information). The 1998 ML 6.2 Rueyli earthquake is taken as a case study.
First, we reconstruct the seismogenic structures. We used the collapsing method to adjust the locations of the Rueyli earthquake aftershocks sequence (579 earthquakes have been used herein). This provides us more accurate locations for the earthquakes. Then we establish the seismogenic structures by using GOCAD software, a 3-D modeling software. Second, we reconstruct the subsurface fault structures based on available geological data. By comparison of two structures mentioned above, we thus discuss the relationship between the 1998 Rueyli earthquake and the Tachienshan fault system.
Two seismogenic surfaces of the Rueyli earthquakes are identified: one is a shallower and flatter surface, dipping 10° to east; the other is deeper and steeper, striking NW to SE and dipping 60° to 70° to northeast. The main shock is located near the conjunction of these two surfaces at the depth of about 7 km. The subsurface structure geometry shows that the Tachienshan fault consists of three main fault surfaces. The first one is the main ramp, striking to NNE and dipping 30° to SE. The second one is the lateral ramp, striking NW and dipping 30° to 50° to NE. At about 6 km deep, both ramps extend and connect to the flat or the decollément (the third fault surface of the Tachienshan fault), which strikes N-S, dipping 6° to east. The main shock is also located around the conjunction point where the lateral ramp connects to the flat. Based on the geometric relationships, the seismogenic structures of the Rueyli earthquake are closely related to the Tachienshan fault system. The focal mechanism of the main shock and the distribution of the aftershocks indicate that the Rueyli earthquake might release the energy on the lateral ramp and propagate northward to the main ramp.
In this study, we successfully built up the seismogenic structure model by the distribution of aftershocks. In addition to the geological structure model, the geotectonic characteristics can be understood in more details.

第一章緒論 1
1.1研究動機與目的 1
1.1.1　研究動機 1
1.1.2　研究目的 3
1.1.3　1998年瑞里地震簡介 3
1.2主要地質構造 6
1.2.1　大尖山斷層 6
1.2.2　鹿窟斷層 6
1.2.3　觸口斷層 8
1.2.4　水社寮斷層 8
1.3前人研究 8
第二章研究方法之簡介 13
2.1研究流程 13
2.2聯合震源定位法 15
2.3震源位置疊合法 16
2.3.1　地震定位的準度與誤差 16
2.3.2　震源位置疊合法之基本原理 16
2.3.3　震源位置疊合法的處理步驟 17
2.4GOCAD 18
第三章資料之蒐集及前處理分析 20
3.1瑞里地震之資料蒐集與處理分析 20
3.1.1　資料蒐集與篩選 20
3.1.2　震源位置疊合 20
3.1.3　載入GOCAD的前處理 23
3.22D及3D地震及地質剖面的分析及建立 24
3.2.1　研究平台 24
3.2.2　建立瑞里地震分布構造模型 24
3.2.3　利用2D資料建立3D模型 28
第四章瑞里地震模型及大尖山斷層模型的建立 32
4.1瑞里地震分布之構造模型 32
4.2大尖山斷層之地質構造模型 39
4.2.1　大尖山斷層模型（1） 41
4.2.2　大尖山斷層模型（2） 44
第五章地震模型及地質模型的比較及討論 48
5.1地震構造模型與地下斷層構造模型的比較 48
5.2震源機制解與大尖山斷層模型 52
5.3地震可能造成的破裂面積 53
5.4地震定位之誤差及問題 59
5.5地震分布構造面對地下構造之貢獻 59
第六章結論 61
參考文獻 63
附錄一　瑞里地震原始資料 66
附錄二　Vset格式範例 75

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