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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/65207


    Title: 2012霧台地震同震變形及震源區應力狀態分析;Fault modeling of the 2012 Wutai, Taiwan earthquake and its tectonic implications
    Authors: 蔣盼忻;Chiang,Pan-hsin
    Contributors: 地球科學學系
    Keywords: 2012霧台地震;GPS同震位移;斷層滑移模型;應力狀態
    Date: 2014-07-28
    Issue Date: 2014-10-15 14:43:16 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 2012年2月26日台灣屏東霧台附近發生芮氏規模6.1的霧台地震,地震震源機制解顯示此地震為逆斷層帶少許走滑分量。霧台地震震央位置與2010芮氏規模6.4的甲仙地震相距只有25公里,且兩者震源深度接近 (~25公里)。為了瞭解霧台地震斷層滑移在三維空間中的分佈情形,本研究使用GPS觀測的同震位移資料以及彈性半空間模型,逆推霧台地震的同震滑移模型。GPS觀測之同震位移在水平方向大約有1~7 mm,誤差約1~4 mm。而垂直位移最大抬升量有6 mm,最大下降量約5 mm,誤差範圍在4~11 mm。逆推得到的最佳斷層參數為:斷層長寬各30 公里,斷層深度16.5公里,走向是310 º向東北傾30 º。斷層面上每個子斷層逆衝滑移量約15~78 mm,左移分量為1~21 mm。最大滑移量是81 mm,出現在深度約20~25公里的地方。霧台地震的破裂面並未與任一地表已知斷層有關,而霧台地震與甲仙地震震源機制解類似,且震央距離接近,因此推測霧台地震與甲仙地震是由於此區域的東北-西南向壓應力,造成兩個相似且重複出現的地震。
    根據GPS速度場計算地表應變率顯示:本區主要受到東-西方向之伸張作用,此現象與地震觀測相符合,在淺部以正斷層型態地震為主。然而,霧台地震與甲仙地震皆為深度較深的逆斷層,表示此區在上部地殼與下部地殼受到不同的應力狀態。此區域在上部地殼可能受到山脈重力崩解,造成淺部地區受到伸張應力,到了下部地殼,山脈重力的影響減弱,因此在較深的地區主要還是受到板塊擠壓為主導的應力狀態。
    此外,根據不同型態的地震數目在深度變化的分析,由正斷層為主轉變為逆斷層為主的深度約為10公里。而走向滑移型態的地震數目不論在淺部,或是深度大於十公里的地方都有一定數量存在。由以上結果可推測,在深度超過10公里的地方σ3與σ2的值會很接近,這兩個主應力方向容易互換,因此可以同時觀察到逆斷層與走向滑移斷層型態的地震。隨著深度越來越淺,σ1與σ2會很接近,所以能夠同時觀測到正斷層與走向滑移斷層型態之地震。而深度10公里的轉變交界處之最大主應力 (σ1) 與最小主應力 (σ3) 的值會非常接近,代表在深度10公里處的軸差應力接近於零。
    ;On 26 February 2012, an ML 6.1 earthquake occurred near Wutai, southern Taiwan, at a depth of 26 km. The epicenter located at 25 km south of the March 2010 Jiashian, Taiwan earthquake (ML 6.4). We employ an elastic half-space dislocation model and GPS coseismic displacements to invert for the optimal fault geometry and slip distribution of the Wutai earthquake. We estimate GPS coseismic displacements from the differences of three-component time series of station position prior to and post the mainshock. The maximum amplitudes of both horizontal and vertical displacements are less than 10 mm. Our preferred fault plane strikes 310º and dips 30º to NE, with reverse slip of 15~78 mm and left-lateral slip of 1~21 mm. The Wutai rupture is not related to any known geologic structure, but the fault geometry and focal mechanism are in line with the 2010 Jiashian rupture.
    Surface strain rates adjacent to the Wutai rupture show a regional extension, consistent with pervasively normal-faulting earthquakes at depths shallower than 10 km in the southern Central Range. Earthquake focal mechanisms at greater depths, including Wutai mainshock, show predominately thrust-faulting. Variations of fault types from normal- to thrust-faulting near 10-km depth reflect the effect of the gravitational collapse at shallow depths and a nearly zero differential stress at the transition depth.
    Appears in Collections:[地球物理研究所] 博碩士論文

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