利用微地動場址特性擬合技術推估台北盆地S波速度構造

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Title:	利用微地動場址特性擬合技術推估台北盆地S波速度構造
Authors:	林晟毅;Lin,Cheng-Yi
Contributors:	地球科學學系
Keywords:	台北盆地;微地動;單站頻譜比;S波速度;場址效應;Taipei Basin;Microtremor;H/V Ratio;S-wave Velocity;Site Effect
Date:	2014-07-08
Issue Date:	2014-10-15 14:43:08 (UTC+8)
Publisher:	國立中央大學
Abstract:	台北盆地由於其第三紀基盤形貌及鬆軟的近地表沖積層，盆地內場址效應所造成的地震波放大和震動歷時延長成為地震災害之主因，如2002年3月31日花蓮外海地震，造成盆地內震度達到五級。台北盆地內之地層速度分佈及構造形貌已有許多研究成果，林（2009）利用接收函數分析盆地內TSMIP強震站地震資料，推估其淺部地層S波速度構造形貌，清楚描繪出盆地內基盤深度及其上主要地層之深度分佈。然而，有限的測點分佈造成空間解析度較為不足，尤其是對於地層速度變化較大的近地表部分，仍須有更為詳細且能實際反應其場址特性變化之地層速度資訊。台北盆地內現已有密集的微地動單站頻譜比（H/V Ratio）分析之場址特性變化資料，至少每1公里有一測點，共計589點。因此，本研究規劃利用此密集場址資料進行近地表S波速度推估；利用已知近地表速度（強震站鑽探、微地動陣列、接收函數及震測等資料）位置作為控制點，配合發展完成之基因赫氏法（GA-Haskell method），擬合各微地動測點之微地動單站頻譜比，求得各微地動測站之一維速度構造，推估反應其場址特性之近地表S波速度變化，並與已知之地質與地物實際觀測資料比對修正，藉由密集分佈在盆地內的測站分佈，進而彙整所有結果，建立完整且細緻的台北盆地近地表S波速度構造之三維形貌。此實際反應盆地內鬆軟地層場址特性之速度模型，將是未來地動預估或模擬之重要參考，提供更為精確之近地表地層控制。 ;The Taipei basin is a triangular alluvium basin. Because of the complex Tertiary basement and the weak Quaternary alluvium, the site effects of the basin amplifying and extending the seismic waves are the major reason of seismic disasters in Taipei. The detailed and correct velocity model is necessary for the ground motion estimation. The velocities and structures of the strata in Taipei basin has been studied repeatedly by various surveys and analyses. However, the most of the existing velocity structures for the near-surface part which varies significantly in Taipei basin are simple and insufficient. The more detailed near-surface velocity structure reflecting the real and complex seismic site-effects of the Taipei basin is necessary. The detail site response all over the Taipei basin has been studied by using the H/V ratios of dense microtremor surveys. According to the previous results, this study will evaluate the near-surface S-wave velocity by the simulation of the microtremor H/V ratios based on the GA-Haskell method we developed in the Taipei basin. The numerous microtremor data are helpful to figure the S-wave velocity and thickness of the Sungshan Formation or the other deeper formations which control the seismic site-effect in the basin. Finally, the complete and detail near-surface S- wave velocity model for the Taipei basin will be establish. It will be helpful to the strong motion prediction and simulation in the future.
Appears in Collections:	[Graduate Institute of Geophysics] Electronic Thesis & Dissertation

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