https://scholars.lib.ntu.edu.tw/handle/123456789/37521
標題: | 台灣東部地區淺源地震再定位及其構造含意之探討 | 其他標題: | Relocation of the crustal earthquakes in the eastern Taiwan and its tectonics implication | 作者: | 吳逸民 | 關鍵字: | 地震;震源機制解;地體構造;台灣東部;板塊分界;Earthquake;Focal mechanism solution;Tectonics;EasternTaiwan;Plate boundary | 公開日期: | 2004 | 出版社: | 臺北市:國立臺灣大學地質科學系暨研究所 | 摘要: | 為了了解台灣東部區域的構造意 含,此研究中對於中央氣象局地震目錄 中東部地區的6173 個地震做重新定 位,並製作33 個ML ≥5.0 的震源機制 初動解。從研究結果顯示,此地區地震 分佈與震源機制解有相當的吻合度。縱 谷斷層為一向東傾的地震板塊縫合 帶。在縱谷斷層以西,中央山脈地區為 淺層地震分布並為有張裂型態的震源 機制解。然而在縱谷斷層以東,大多數 的地震為具有逆衝性質型態的震源機 制尤其在南部地區(23.5°N 以南),而在 北部地區兼具滑移與張裂型態的震源 機制解,分布較為複雜。台灣東部的地 體構造可分為南北兩半部,其分界約為 23.5°N 垂直縱谷的走向(N110°E)。在南 部地區,從地震分布可以看出為一向東 傾的板塊分界,且震源機制解也吻合此 一板塊邊界分布(約N25°E 向東傾54 度 ),此區域的地體構造較為單純,歐 亞板塊向東隱沒至菲律賓海板塊下。在 北部地區,構造較為複雜,因歐亞板塊 向東傾,而菲律賓海板塊向西且有擾曲 的現象,因而在此區域外海有淺層帶有 張裂型態的地震分布。 We relocated 6173 shallow earthquakes and determined focal mechanism solutions of thirty-three ML ≥ 5.0 events in the eastern Taiwan region (bounded by 22.7 N, 120.8 E ; °° 24.5 N, 121.5 E; 24.3 N, 122.3 E °°°° and 22.5 N, 121.6 E) in order to °° investigate their tectonic implications. Our results suggest that the distribution of the relocated earthquakes generally agrees with the fault plane determined from the focal mechanism solutions. The Longitudinal Valley (LV) is an east-dipping seismic suture zone that separates two different tectonic regions. On the left-hand side of the LV, shallow earthquakes and normal fault-type focal mechanism were found in the Central Range region. But on the right-hand side of the LV, most events occurred in the Philippine Sea Plate (PSP) were of the thrust-type, especially for the south portion and a few normal and strike-slip focal mechanism events were observed in the north portion. The tectonics of the eastern Taiwan can be classified from south and north into two regions, and there may exist a structure or boundary at about latitude 23.5°N with a strike of N110°E. In the northern portion of the eastern Taiwan, the plate boundary appears to be an east-dipping plane defined by the earthquake distribution. The focal mechanism solutions determined in this zone show thrust type faulting and agreed with this boundary plane (strike N20°E and dip about 50°). In this region, the Eurasia Plate (EP) dips to the east, and the PSP bends and dips to west. Thus, the shallow earthquakes with normal and strike-slip focal mechanism were observed in the offshore area of this region. On the other hand, the southern part of the eastern Taiwan is a simple tectonics condition. The EP subducts to the east under the PSP. The LV is a suture zone dipping to the east, and most events occurred on the right-hand side of the LV. Focal mechanism solutions of these events were thrust-type with strike about N25°E and dip 54° to the east. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/11854 | 其他識別: | 922119M002026 | Rights: | 國立臺灣大學地質科學系暨研究所 |
顯示於: | 地質科學系 |
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922119M002026.pdf | 231.41 kB | Adobe PDF | 檢視/開啟 |
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