屏東麓山帶的潮州斷層為台灣主要的南北向斷層之一，此一斷層位於台灣南部，介於屏東平原的東邊與中央山脈之間，以往的研究資料推測此斷層為一高角度向東傾斜的斷層。本研究針在屏東麓山帶區域，北緯22.36~22.81度，東經120.44~120.82度，以中央研究院地球科學研究所於2001年8月至2002年1月間，在潮州斷層附近佈下的24個臨時地震測站，利用六個月內所獲得的地震觀測資料，挑選品質較佳的142個地震，共1528個P波走時與1385個S波走時，利用SIMULPS12進行重新定位與逆推地下速度分布，得到潮州斷層附近區域之上部地殼三維速度構造，本研究結果顯示，不論藉由深度分層或垂直剖面的速度構造，皆可由明顯的高、低異常區判斷潮州斷層確實存在。且由斷層東側呈現的高區與西側的低區，判斷潮州斷層為逆衝斷層。由地震分布圖中研判，沿著斷層並無明顯的地震集中，推測潮州斷層沒有劇烈的活動。根據地震重新定位後的變化與分布，加上稍低的地震個數來看，屏東麓山帶的地震活動並不活躍，故推測本研究中所觀測到的地震可能是由於較大尺度且緩和的構造活動所造成。 The Chaochou fault in the Pingtung area is one of the most important faults in southern Taiwan, and is located between the Pingtung Plain and the Central Range. According to previous studies, the Chaochou fault is considered to be a high-angle fault that dips eastward to the Central Range. From a tectonic point of view, regional stresses in the Pingtung area are controlled by two tectonic forces. The first force is the compressional stress related to the arc-continent collision between the Philippine Sea Plate and the Eurasian Plate; the second is the extensional stress related to the opening of the South China Sea to the South. Under these two mechanisms, the crustal structure beneath the Pingtung area has a complex formation. However, in examining earthquakes greater than magnitude 3 that occurred in the years between 1991 and 2001, we discover that the seismicity in southwestern Taiwan in this period was low. The question as to why this is the case is what first inspired our interest in studying this particular area. This study makes use of data collected by the Institute of Earth Sciences, Academia Sinica between August 2001 and January 2002 at 24 temporary seismic stations located near the Chaochou fault, as well as velocity structures collected through tomography in the foothills of the Pingtung area. We hope that this study will teach us more about crustal structure of this area and will enable us to understand the reasons for low seismicity there.
