泥貫入體構造對恆春西台地及附近海域之地體構造演化影響

恆春西台地的地層微向東傾，以往研究推測在其西側海域有一向東傾斜的逆衝斷層存在（西海岸斷層），因該斷層抬升造成恆春西台地東傾。為釐清恆春西台地的地體構造問題，本研究分析了多頻道反射震測和精密水深資料，並進行陸上地質調查。經研究分析發現前人所推測之西海岸斷層並不存在，取而代之的是泥貫入體構造。因該泥貫入體的抬升，造成位在泥貫入體東翼之恆春西台地的地層向東傾。本研究另發現恆春斷層有延伸進入海域，在海床有明顯線型構造，且地層被嚴重擾動，顯示該斷層應還在活動中。而在南灣海域也發現因泥貫入體抬升造成的正斷層，命名為「南灣斷層」。由於南灣斷層在海床上造成明顯的線型，錯動珊瑚礁海床，並在海床上造成大量逸氣現象，顯示南灣海域之泥貫入體還是持續在活動中。

關鍵字

泥貫入體；恆春西台地；恆春斷層；南灣斷層

並列摘要

The West Hengchun Hill (WHH) is characterized by gentle eastward-dipping strata that were inferred to be associated with an eastward-dipping thrust (W fault) located at in the offshore area to the west of the WHH. In order to understand the tectonics around the WHH, we have analyzed the multichannel seismic reflection (MCS) and multibeam bathymetric data, and have also carried out onshore investigations. As a result, we have found a mud diapir instead of a thrust in the nearshore area to the west of the WHH. On the basis of the MCS profiles, the WHH is located along the eastern flank of a mud diapir. It indicates that the eastward-dipping strata of the WHH are ascribed to the uplift of a mud diapir. We also identified that the Hengchun Fault extends from the onshore to the offshore area. Based on the multibeam bathymetry and MCS profiles, the offshore extension of the Hengchun Fault shows an obvious structural lineament at seabed and the strata are disturbed along the fault zone. It indicates that the offshore Hengchun Fault is still active. For the first time, we have identified a normal fault named ＂Nanwan Fault＂ in the Nanwan water. The Nanwan Fault is located on top of the mud diapir and was caused by the uplift of mud diapirism. The Nanwan Fault dislocated the coral reef seabed and many gas plumes were observed from the seabed of the mud diapiric intrusion area. It indicates that the mud diapirism is active in the Nanwan water.

並列關鍵字

mud diapir ； West Hengchun Hill ； Hengchun Fault ； Nanwan Fault

國際替代計量

泥貫入體構造對恆春西台地及附近海域之地體構造演化影響

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