南极布兰斯菲尔德海峡区域重力场特征及异常分析

摘要

南极布兰斯菲尔德海峡及周边区域是南极大陆火山、地震等新构造活动最活跃的地区,与南设得兰海沟、南设得兰群岛一同构成南极大陆边缘现存唯一的"沟-弧-盆"构造体系.本文基于"雪龙"船第28、第30航次实测数据及两个航次的国际共享资料,利用均衡改正数据处理方法获得布兰斯菲尔德海峡的莫霍面深度及其分布规律,分析深部构造-断裂的区域分布及其重力异常特征等.布兰斯菲尔德海峡内的空间重力异常呈条带状分布,走向总体与地形相近,布格重力异常则由两侧向中间升高,大致在坡折处形成异常场值为100×10-5 m/s2的分界线,在中央次海盆和东部次海盆海山处形成两个异常高值圈闭,异常值最高为150×10-5 m/s2.莫霍面深度以弧后扩张中心为最低值,向南设得兰群岛和南极半岛两个方向递增,深度从12 km递增至陆坡位置的24 km.%Bransfield Strait and its surrounding areas are the most active neotectonics region of volcanoes and earth-quakes,which constitute the only existing "trench-arc-basin"system together with the South Shetland Trench and South Shetland Islands.Based on the observed data from the 28th,30th Antarctic expeditions and the international public data,this study takes use of the isostatic correction method to invert the Moho depth and its distribution characteristics.The gravity field anormaly of the deep tectonic was analyzed.The free-air gravity anomaly shows a strip-like distribution,orienting closely to the terrain.The Bouguer gravity anomaly in the strait rises up from both of the two sides to the middle.Two high-value-anomaly traps appear in the central trough and the seamounts in the eastern trough respectively,with the highest value up to 150×10 -5 m/s2 .The minimum value of Moho depth (12 km)appears in the back-arc spreading area.The depth gradually increases from the back-arc spreading area to the both sides (e.g.,Bransfield Strait and Antarctic Peninsula),and reaches 24 km at the slope area.