臺灣西南海域泥貫入體抬升及天然氣水合物解離所引發的大型海底山崩

A Large Submarine Landslide Triggered by Mud Diapirism and Gas Hydrate Dissociation Offshore Southwest Taiwan

陳松春(S.C. Chen) ； 蔡慶輝(C.H. Tsai) ； 許樹坤(S.K. Hsu) ； 王詠絢(Y.S. Wang) ； 葉一慶(Y.C. Yeh) ； 劉家瑄(C.S. Liu)

《鑛冶：中國鑛冶工程學會會刊》 61卷3期 (2017/09) Pp. 33-46

https://doi.org/10.30069/MM.201709_61(3).0003

摘要

根據反射震測及多音束水深資料，在臺灣西南海域首次發現1處大型海底山崩，命名為「枋寮山崩」，枋寮山崩位於枋寮峽谷西側的大陸斜坡，分布水深約420~900公尺，枋寮山崩的海床呈現約1˚ ~ 2˚的平緩地形。山崩長度約15公里，寬度約10公里，估算崩塌體積約26平方公里，山崩頂部崩崖位在泥貫入體MD7-1的南翼，崩崖高度約30公尺，東側邊界為斷層A，西側邊界為斷層C及D，山崩區域可分為5階的階地地形，顯示有數次的潛移活動。依據地形，可將崩塌地劃分為上部段及下部段，分界水深約600公尺，此深度為臺灣西南海域天然氣水合物賦存的最小水深。崩塌形成的機制和泥貫入體MD7-1的抬升有關，而下部段則再受到天然氣水合物解離的影響，造成下部段的海床地形比上部段更崎嶇不平。

關鍵字

海底山崩 ； 泥貫入體 ； 天然氣水合物 ； 臺灣西南海域

並列摘要

Based on seismic reflection profiles and multi-beam bathymetric data, a large submarine landslide named Fangliao Slide offshore SW Taiwan is identified for the first time. The Fangliao Slide occurred on the continental slope to the west of the Fangliao Canyon at water depth between 420 m and 900 m. The seafloor of the Fangliao Slide has a gentle slope with dipping angle 1° to 2°. The landslide covers an area of ~15 km long and ~10 km wide and has a bulk volume of ~26 km3. The headwall of the landslide has ~30 m vertical offset at the southern flank of mud diapir MD7-1, and the sidewalls are bounded by fault A in the west and faults C and D in the east. The sliding area has five bathymetric terraces indicating that the slope failures occurred several times. The Fangliao Slide can be divided into an upper domain and a lower domain separated at the water depth of ~600 m where the gas hydrate offshore SW Taiwan dissociated. The initial slope failure of the Fangliao Slide was probably linked to mud diapirism of MD7-1 and the slope failure in the lower domain was probably augmented by the gas hydrate dissociation. The seafloor morphology in the lower domain is therefore more corrugated than in the upper domain.

並列關鍵字

submarine landslide ； mud diapir ； gas hydrate ； southwest Taiwan