利用噪聲成像解析嘉義梅山斷層區域之三維淺層剪力波速度構造;3-D Shear Wave Shallow Crustal Structures at Meishan Fault Zone using Ambient Noise Tomography

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Title:	利用噪聲成像解析嘉義梅山斷層區域之三維淺層剪力波速度構造;3-D Shear Wave Shallow Crustal Structures at Meishan Fault Zone using Ambient Noise Tomography
Authors:	鄭璟郁;Cheng, Ching-Yu
Contributors:	地球科學學系
Keywords:	梅山斷層;噪聲成像;三維速度模型;小梅背斜;密集地震網
Date:	2017-07-21
Issue Date:	2017-10-27 13:16:00 (UTC+8)
Publisher:	國立中央大學
Abstract:	梅山斷層為斗六-嘉義丘陵邊緣之一右移性橫移斷層，在1906年發生的梅山地震（M=7.1）即為此斷層的活動所引發，當時造成三千多人員傷亡及六千多棟房屋倒塌。根據地表地質研究，梅山斷層由梅山鄉向西南延伸至民雄鄉後消失，斷層總長約25公里。在921集集地震之後，臺灣中南部的斷層活動性備受關注，百年來學者們對梅山斷層構造的幾何模型有許多研究，包括地表地質研究以及淺層震測研究，但仍尚未有針對此地區的淺層速度構造作詳盡的分析，因此本研究利用噪訊成像反演梅山斷層附近地區的三維淺部地殼剪力波速度構造。本研究於2015年8月至2015年11月在梅山斷層鄰近區域佈放了100個單分量短週期的Texan儀器(測站間距約為兩公里)，從連續資料中重建兩測站間的雷利波經驗格林函數，並使用了多重濾波法以及影像轉換技術得到群速度和相速度的頻散曲線，相速度可信賴週期大約落在0.6-5.8秒，最後以快速推進法計算在非均勻介質中測站配對的波線路徑與速度，再利用小波為基底的模型參數化方式直接反演得到三維剪力波速度構造。從棋盤格測試結果顯示可信深度可達5公里左右，其速度分布與地表地質還有震測研究結果一致，在本研究結果中也可以觀察到梅山斷層、嘉義盲斷層以及小梅背斜等重要構造的三維幾何型態。;1906 Ｍ7.1 Meishan earthquake occurred near Chiayi city in southwestern Taiwan and resulted in more than three thousands casualties and six thousands of buildings collapsed. Based on the geological survey, the Meishan fault zone a right-lateral strike-slip fault with a length of 25 kilometers, was the main contributor for this event. In previous studies, many researchers have done lot of investigation about the Meishan Fault zone, including geologic researches at surface and seismic explorations at shallow crust. However, there is still limited information about 3-D shallow crustal structure of this study area. Therefore, we deployed 100 Texan instruments (~2 km interval) between Aug. and Nov. 2015, covered around the Meishan Fault zone. We obtained a 3-D shear wave shallow crustal velocity structure using ambient noise tomography. The reliable periods of phase velocity from Rayleigh wave are 0.6 to 5.8 seconds, which correspond to around 0-5 km at depths. The results are consistent with surface geology and seismic explorations study. Furthermore, Meishan fault, Chiayi blind thrust, and Xiaomei anticline near the fault zone are observed from this study.
Appears in Collections:	[Graduate Institute of Geophysics] Electronic Thesis & Dissertation

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