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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/5612


    Title: 利用單站頻譜比法探討集集地震造成之土壤非線性反應
    Authors: 葉俊岑;Jing-Tsin Yie
    Contributors: 應用地質研究所
    Keywords: 集集地震;非線性;單站頻譜比法;Chi-chi earthquake;nonlinear;H/V spectral ratio method;site effect
    Date: 2001-07-20
    Issue Date: 2009-09-22 09:58:08 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 本研究首先使用台灣羅東LSST陣列、花蓮SMART-2陣列以及日本Port Island井下陣列的強、弱震資料,以單站頻譜比法討論該地區非線性放大反應,並利用前人研究結果作為驗證,藉此評估單站頻譜比法進行土層非線性反應之分析之可行性。 在LSST和SMART-2的結果中,可推測非線性反應的發生原因除了PGA值大小,地盤堅硬程度也是一項重要因素。由雙站法得到之頻譜比壓抑放大現象在利用單站頻譜比法進行分析時也可以很清楚的看出。而Port Island井下陣列使用單站法的結果雖然和雙站法不完全相同,但亦能觀察到液化過程中頻譜比變化的情形。由此可知,利用單站頻譜比法來進行非線性反應的研究是可行的,而液化時是否造成土壤非線性的行為,亦可由單站頻譜比法的結果中得知。 由於液化區附近土壤極有可能發生非線性反應,故本研究亦根據液化地區附近的地震記錄,使用單站頻譜比法求出集集主、餘震之頻譜比值以及1998年前之弱震平均頻譜比,且利用強弱震頻譜比的相對變化率,判斷強震時發生非線性反應的程度與範圍,並與前述液化區之範圍進行比對,所得結論如下: 1. 根據各測站在3 ~ 20 Hz間平均相對頻譜比分布情形,發現非線性反應多發生於鬆軟沖積層地帶,而液化區周圍則更有高度非線性反應。大部分的線性放大區域都位於西部麓山帶地質區。台中盆地底下以礫石層為主,在本結果中亦無非線性作用發生。總括來看,3 ~ 20 Hz間發生的非線性範圍與程度和液化分布相關,與地質分區亦有關連。 2.餘震時非線性現象較明顯的的地區依舊以西部的鬆軟沖積層為主,非線性範圍及程度皆不如主震,多數測站還是呈線性放大。 3.我們計算3 ~ 20 Hz內非線性程度最大的頻帶的平均變化率,結果較能突顯各地區非線性的程度,更具有實際參考價值。 4.研究結果發現,某些地區由於位在沖積平原上,主震時造成高度非線性現象,但並未傳出液化災情;員林鎮、台中港、伸港鄉和斗南鎮等位於濱海平原地質區的液化區,皆有很強的非線性大放效應;而埔里盆地和南投市等發生液化的地區處於西部麓山帶,其非線性現象則較不明顯。顯示發生非線性反應的地區不表示當地土壤發生液化現象,但是土壤液化時應會造成土壤的非線性反應發生。當地震發生時,會造成土壤非線性效應或是液化應是取決於PGA值的大小和地層因素。 5.根據不同液化地區附近測站的頻譜比結果來看,土壤液化不一定會造成所有頻段的放大倍率降低,而只有某特定頻段的放大倍率產生變化,且各地區變化的頻段不盡相同。 On September 21, 1999, an earthquake with the magnitude of 7.3 on the Richter scale occurred in the central Taiwan. The surface rupture along the Chelungpu fault is about 100 km in length. The earthquake killed more than 2,500 people and completely destroyed more than 10,000 buildings, and left 100,000 people homeless. The Chi-chi earthquake not only directly caused heavy damages on the structure and huge human life loss near the epicenter area, but also induced the secondary damages to the buildings in the central Taiwan region. From the field surveys, many places, such as Yuanlin, Wufong, Nanto City and Puli, suffer considerable from the soil liquefaction. It implies that the nonlinear soil response should occur pervasively in the central Taiwan area. The aim of this study is to identify the area have nonlinear soil response during the Chi-chi earthquake. The data we use include main shock, after shocks of the Chi-chi earthquake and the weak motion records before the Chi-chi earthquake. We use the horizontal-to-vertical (H/V) spectral ratio method to conduct the analysis in this study because of lacking a good referent rock site in the alluvial plain. From our results, we found the nonlinear soil response usually occurred in soft alluvial plain, especially at the site near liquefied area. Most linear amplification areas are observed in the western foothill and Taichung Basin. The range and degree of nonlinear soil response are highly related to the local geology. Besides, we also use the data from three downhole accelerometer arrays to check the accuracy of nonlinear soil response that estimated from H/V spectral ratios. The results strongly suggest that we can use the H/V spectral ratio method to estimate the nonlinear site effect.
    Appears in Collections:[應用地質研究所] 博碩士論文

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