Title

利用寬頻線性地震網資料研究2006年台東地震之發震構造與地震活動

Translated Titles

A Study of Subsurface Structures and Seismicity of 2006 Taitung Earthquake by Using Linear Seismic Network Data

DOI

10.6342/NTU.2008.02881

Authors

顏郁捷

Key Words

地震重定位 ; 雙差分定位法 ; 三維測站修正法 ; relocation ; double-difference relocation ; three dimensional velocity combined with station correction

PublicationName

臺灣大學地質科學研究所學位論文

Volume or Term/Year and Month of Publication

2008年

Academic Degree Category

碩士

Advisor

黃柏壽

Content Language

繁體中文

Chinese Abstract

長久以來,中央山脈斷層是否存在與其活動型態一直是個爭論的議題。由於該斷層在縱谷最南段可能是以盲斷層的形式活動,在野外很難直接找到露頭加以量測,故無法直接證實此中央山脈斷層的存在。適逢2006年4月1日在鹿野附近,發生了規模6.2的地震,震源機制解顯示是一高角度的左移走向橫移斷層並帶有微量的逆斷層分量。由於此次主震的震央非常靠近前人認為的中央山脈斷層的位置,且斷層型態也與縱谷斷層系統大相逕庭。因此2006年台東地震提供了難得的訊息,有助於我們了解縱谷最南段活動構造在深部的形貌。台灣東部受限於測站不足且分佈不平均,往往造成地震定位上的誤差。因此,本研究企圖以氣象局到時資料為基礎,並額外加入寬頻線性地震網的到時資料,並以三維測站修正法和雙差分定位法重定位,希望藉以改善測站因素造成的定位誤差。本文所使用的新資料,選取自中研院在2005年4月中旬正式啟用的寬頻線性地震網,該地震網橫跨台灣南部,共有SL01~SL25等25個測站,西起雲林,東至台東,其走向大致垂直於台灣主要的地體構造單元,而線性地震網特意的排列方式,能提供水平方向上較佳的約制。單點定位法得到的水平向誤差,從線性地震網資料加入前的2.56公里,降低為加入後的1.47公里。根據本研究得到的定位結果顯示,本研究區域內主要有兩個地震群,一是沿著鹿野斷層和中央山脈東麓分佈的中央山脈地震群,發震時間集中在4月1日到4月4日;一是呈西北向分佈的外海地震群,發震時間集中在4月15日到4月16日。線性地震網資料加入後,我們發現中央山脈地震群可以細分成東、西兩個近乎垂直的次地震群;另外,在鹿野斷層北段底下,有一向東傾約45°的淺部地震群覆蓋在中央山脈地震群之上。外海地震群約在深度17公里處出現轉折點,17公里以上呈現約向東傾60°,17公里以下則呈現約向東傾45°,代表該地震群在深部呈現淺陡深緩的幾何形貌。再以強震站和線性地震網P波初動的資料,解算規模大於3.5之地震事件的震源機制解,發現東、西兩個次地震群的震源機制呈現不同的型態,西次地震群(包含主震在內)主要以高角度走向滑移為主,而東次地震群則以逆斷層為主。在鹿野斷層北段底下的淺部地震群以逆斷層為主,此為鹿野斷層活動所致;而外海地震群則是以逆斷層為主,這與一般對於縱谷斷層的認知吻合。

Topic Category 基礎與應用科學 > 地球科學與地質學
理學院 > 地質科學研究所
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