前人根據龜山島上的熔岩流分布研究指出龜山島近 7000 年來至少發生過四次火山噴發事件。除此之外，火山島的噴發事件也常和伴隨的火山側翼崩塌事件有關。龜山島周圍的高精密水深資料顯示海底有岩屑崩落（Debris avalanche），主要分佈在北方以及南方的海域。為瞭解崩塌機制與岩屑崩落的分布情形，本研究主要利用高精密水深、底拖側掃聲納、底質剖面與火花放電波源的震測剖面等資料來研究北方海域崩落事件。水深資料的分析結果顯示岩屑崩落分佈在距離龜山島北側翼的馬蹄鐵狀崩塌口約4公里遠且占據大約 10 平方公里的面積，可辨認出的崩落石塊約有67處，呈現不規則分布且高度約為10到 50 公尺高。從 ROV 觀測的結果發現，研究區域的海床主要以泥質和沙質為主的沉積環境，而且為大小不一的石塊堆疊而成並附著了珊瑚礁等生物在石塊上。 除此之外，震測資料分析結果可大致區分為兩個不同的混亂震測相，第一個混亂震測相主要包含了反射訊號的繞射現象以及不連續的側向反射訊號，本論文定義其為第三個大量沉積物傳輸的堆積單元(MTD3)。至於第二個混亂震測相主要包含不規則的側向反射訊號以及斷斷續續的強振幅反射訊號，以深度分別可定義為第一個和第二個大量沉積物傳輸的堆積單元 (MTD2 和 MTD1)。震測相與分布的情況來看，與島上崩塌口相關的崩塌沉積物主要為 MTD2 和 MTD3。MTD3主要分佈於淺部地層中，在龜山島斜坡地區覆蓋了大約90公尺厚的沉積物 並往東北方向傳遞。另外在 MTD3 的地層中可以進一步辨識滑動不整合面(U3)。因此，根據分佈的特性以及不整合面的位置推測出 MTD3 可能來自於龜山島海底邊坡不穩定所造成的崩塌事件。至於 MTD2 的分布位置主要在較深部的地層中(約為350 ms TWT)且呈現連續的強反射訊號，顯示其質地可能為較硬的岩塊，因此推斷龜山島側翼崩塌事件主要是記錄在 MTD2。最後，本研究提出一個模型來解釋龜山島側翼崩塌以及後續的海底山崩事件。 最後，本研究提出一個新的模型來解釋龜山島側翼崩塌以及後續的海底山崩事件。;Based on the ignimbrite layers, previous studies suggested that Kueishantao volcanic island has probably erupted four times in the past 7000 years. Many studies have also shown that volcanic eruptions may be highly related to flank collapse events. New multi-beam bathymetric data around Kueishantao volcanic island have revealed the distribution of submarine debris avalanches in the north side. In order to better understand the landslide mechanism, we have studied the northern part of the debris avalanches distribution with marine geophysical data. Using the multi-beam bathymetric, sub-bottom profiler, sidescan sonar, remotely operated vehicle (ROV) dives data and sparker seismic reflection profiles, we have identified the blocky deposits of a debris avalanche. The debris avalanche is probably related to the horseshoe scar of a volcanic flank collapse. The debris avalanche had a runout distance up to 4 km northeastward and has covered about 10 km2 of hummocky terrain with individual blocks range from ~10 m to ~50 m high. The chaotic facies distinguished from the sparker seismic profiles can be divided into two types. The first type contains diffraction hyperbolae reflections and broken or discontinuous lateral reflections, which are interpreted as mass-transport deposits unit 3 (MTD3). The second type contains irregular lateral reflections and broken high- amplitude reflections, which are interpreted as mass-transport deposits unit 2 and unit 1 (MTD 2 & MTD 1), respectively. The main landslide deposits recognized from the chaotic facies are related to MTD2 and MTD3. In general, MTD3 is distributed in the shallow strata with thickness up to 90 m at island slope area. The high-resolution SBP profiles indicate that fine-grained sediments are distributed at island slope and have strong reflections with less sedimentation over the hummocky deposits area. Moreover, a sliding plane unconformity U3 is recognized from the seismic profiles within the MTD3. Hence, MTD3 could be induced by a slope slumping event and has contributed the recent morphological features. MTD2 is mainly distributed to the NE of the island and is buried in the deeper strata with strong reflection material. Cross-section seismic profile line64 indicates that MTD2 can be traced from the Kueishantao Island to downslope. Hence, MTD2 could be associated with the initial flank collapse event. A new model is proposed for the flank collapse event of the northern Kueishantao Island and a slope slumping event afterwards.
