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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/5380


    Title: 台灣中西部地區之強震特性;Strong Motion Characteristics in West-Central Taiwan
    Authors: 張添炮;Tian-Pau Chang
    Contributors: 地球物理研究所
    Keywords: 反應譜;反應譜比;測站分類;地動參數;設計譜;site classification;ground motion parameter;seismic design spectrum;response spectral ratio;response spectrum
    Date: 2003-05-12
    Issue Date: 2009-09-22 09:52:54 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 本研究選用中央氣象局強震網1995至1999年間8個規模大於5.3的大型地震記錄,先用水平(H)與垂直(V)分量反應譜比的方法,將測站屬性由堅硬至鬆軟分為A、B、C三類,接著再從地震規模大小、震源深淺、距離遠近以及測站類型等角度,分析台灣中西部地區的強震特性。藉由其它遠場地震的比較把集集主震近斷層的特性呈現出來,並和其他相關研究比較。 研究顯示不同規模、深度、距離的地震記錄,在同一測站上所求出的反應譜比很類似;H/V方法所作的測站分類和實際地質資料相當吻合。H/V圖形的顯著頻率隨著測站類型從A至B至C逐漸降低,而主放大值則逐漸增加;集集主震的H/V圖形比其它地震偏向低頻,主放大值比其它地震稍小。 在同一地震中,當震源距離接近時,三類測站的反應譜在短週期區相差不大,在長週期區則有較大的差異。當震源距離從近變遠只相差不到30公里的情況下,反應譜的整個外觀並沒有太大的改變。但是在不同地震之間,即使地震規模相當,在相同距離之下所得到的反應譜之差異程度,比同一地震中不同類型測站的差異還大。因此本研究認為在相同距離之下,震源效應對於反應譜的影響程度大於測站效應。 本研究8個地震之平均正規化反應譜和其他研究接近,集集主震長週期能量則有明顯增強。現行設計譜對於8個地震三類測站之規範都相當足夠,唯對於集集主震靠近斷層區水平分量仍有低估的現象。 v/a和d/v參數在不同地震之間的差異很大;地震規模較大、震源位置較淺、震源距離較遠者,這二種參數就愈大。集集主震比其它地震大很多,其最大地表加速度正規化至1g後的最大地表速度和位移,是其他研究的2至3倍。ad/v2參數則比較沒有規律性。 在較遠距離之下,PGA值大致是鬆軟的C類測站大於堅實的B類測站,其垂直(V)與水平分量(H)比值也是C類測站大於B類;PGV不明顯。從全部測站的總平均值來看,規模較大的地震PGA之V/H比值大於規模較小的地震,PGV則不明顯。集集主震的PGA以及PGV之V/H比值不僅比其它地震來得大,而且也超過一般工程界所用的2/3。 最大反應值相對於最大地表振動值的放大倍數,大致都介於2和3之間。集集主震跟其它地震比較起來,也沒甚麼特別之處。 In this paper, the accelerograms recorded by the network of Taiwan Strong Motion Instrumentation Program of the Central Weather Bureau are used to analyze the strong motion characteristics in west-central Taiwan. The data consists of 9 earthquakes with ML>= 5.3 occurred in Taiwan area between 1995 and 1999. Firstly, the station sites are classified into three types by their spectral ratios of horizontal to vertical components(H/V) and geological data, from hardness to softness, called type A, B and C respectively. Then, the strong motion characteristics in regard to source magnitude, depth, hypo-distance and site type are analyzed. In order to highlight the near-fault effect during Chi-Chi mainshock, several kinds of comparisons have been made. The results are summarized below: The H/V spectral ratios at the specific site calculated from different events are very similar, implying that the H/V ratios are more independent of source magnitude, depth and path at a specific site. Also, the classification results obtained by H/V method are compatible with geological data. For any event, the dominant frequency of H/V spectrum decrease gradually with the site type from A to B to C, but the dominant amplification factor is increased. Of the Chi-Chi mainshock, its dominant frequency and amplification factor are the lowest among the 9 events. Within the same event, the response spectra for 3 types of sites are very consistent in short period range, however, those have much differences in long period range. The spectral shape has no significant change as the hypo-distance increased from near to far data group is lower than 30 km. Among the different events, however, the spectral shape has much more differences even for the same type of site as well as the same hypo-distance. Therefore, we can conclude that the source effect has more influence on response spectra than the site effect has. The total means of normalized response spectra calculated from all of 8 events are similar to other study, those from the Chi-Chi mainshock are amplified in long period range. The current seismic design spectrum, anchored at a PGA value of 0.33g, appears to be much adequate for three types of site experiencing the 8 events, and seems to be underestimated, during Chi-Chi mainshock, for site type of A below about 1.2 second. The ground motion parameters, v/a and d/v, have significant variations among the different events. We obtain the larger values of these two parameters from events which have the greater magnitude, shallower depth, and farther hypo-distance. The Chi-Chi mainshock has the largest values of parameters among the 9 events, its maximum ground velocity and displacement, for a unit ground acceleration(1g), are twice to 3 times of the values given by other studies. However, the parameter ad/v2 has no significant trends among the 9 events, they almost lie between 2 and 4. For farther hypo-distance, the softer sites of type C not only have the larger values of PGA but also the larger ratios of vertical to horizontal components(V/H). On the viewpoint of total mean of all station sites, the PGA V/H ratios from events with greater magnitude are larger than those with smaller magnitude, but the PGV is not obvious. Of the Chi-Chi mainshock, its V/H ratios for both PGA and PGV are the largest among the 9 events, these ratios also exceed 2/3 which is commonly used in seismic zone A. The amplification factors of response spectrum related to peak ground motion are almost between 2 and 3, and no exceptions for Chi-Chi mainshock.
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