| 摘要: | 池上斷層位於臺灣東部，為花東縱谷斷層系統的南段，全長約六十七公里，是臺灣地表潛移速率最明顯且快速的一條斷層。此區域是台灣活動斷層活躍的區域，已有不少的大地測量以及地球物理資料，然而先前在池上的反射震測資料（曾彥祺等，2008）最多僅可看到 300 公尺深的資料。故本研究延伸曾彥祺等之研究，利用反射震測以及折射震測的技術於 2020 年 11 月在池上斷層施測三條測線，於萬安村以及錦園村各放置一條超過一公里的東西向測線，使其跨越花東縱谷沖積層以及海岸山脈利吉混同層，而在兩條東西向測線之間放置一條以 Smartsolo地震儀為主的南北向測線，嘗試比較40Hz地耳(geophone)和寬頻的Smartsolo地震儀(5Hz)的特性以及長測線展距進而獲得板塊交界帶下較深層的地層構造影像、池上斷層可能的深度以及淺層的折射速度構造。本研究結果顯示，在錦園村測線剖面中，淺層可以看到層面連續訊號但有受力蟯曲的現象，而在西側探深約500毫秒可看到層面受力褶皺而向東傾之訊號以及其上方有開花構造；而在東側（往海岸山脈方向）可看到訊號連續與不連續之分界，推測為池上主斷層之處，且可看到斷層破裂到深處以及其周圍其他破裂褶皺的訊號。萬安村測線位於斷層上盤，其剖面的淺層較為混亂，有一系列褶皺與開花構造。南北向測線剖面在淺處能看到有明顯的背斜構造，也因Smartsolo寬頻的特性，可在深部看到有層面交角不整合的訊號，整體資料能看到的構造更多，最多可看到的反射訊號可達 800 毫秒，未來深部構造可以多嘗試使用Smartsolo 地震儀進行探測。;Taiwan is located at the collision zone between the Philippine sea plate and Eurasia plate, and the Longitudinal Valley Fault is the boundary fault between these two plates. Chihshang Fault is the southern part of the Longitudinal Valley Fault, it’s about 67 kilometers, it’s the reverse fault and its main active mode is creep. Tseng et al(2010) investigate the two seismic reflection survey line at Chinyuan and WanAn village in Chihshang, but their survey line spacing is short, leading to the investigating depth is not deep. In my research, we try to apply the long line spacing to survey the Chihshang fault area in November 2020, we planned three seismic survey lines: Chinyuan, WanAn, and N-S line. In addition to, we used Smartsolo 5Hz receiver in N-S line expect for greater and deeper data than traditional geophone. In the profile results, In the Chinyuan line, the shallow layer can see the continuous signal of the layer, and there is anticline structure around Chihshang fault and an east-dipping formation is at 500 ms depth (Chinyuan) profile, and there is a flower structure above it; on the east side, the boundary between continuous and discontinuous signals can be seen, which is presumed to be the main of Chihshang fault. WanAn survey line is located at the hanging wall of Chihshang fault, shallow layers of the profile are relatively chaotic, the formation isn’t continuous, and there is a series of flower structures and folding. In N-S survey line, there is a big anticline structure near the Chinyuan survey line. Because of the broadband characteristics of Smartsolo, more structures can be seen in the profile data. The maximum reflected signal can be seen up to about 800 ms, and the signal of angular unconformity can be seen in the deep part. From the profile evidence and the activity direction of the Chihshang area, we surmise that there an anticline structure below the Chihshang area, and we can try to use Smartsolo to detect deep structure for more seismic investigate in the future. |
