The Scotia Arc GPS Project: Focus on the Antarctic Peninsula and South Shetland Islands

该奖项由极地方案办公室南极地质和地球物理方案提供，为继续研究南极半岛和斯科舍海地区的板块运动提供资金和实地支持。最初的“斯科舍弧形GPS项目（SCARP）”的主要目的是确定斯科舍板块相对于相邻板块的运动，并测量沿着其边缘的地壳变形，特别注意南桑威奇微板块和布兰斯菲尔德海峡延伸。本建议的重点仅限于SCARP项目中包括象岛、南设得兰群岛和南极半岛全球定位系统站点的部分。英国南极调查局为该项目提供了斯科舍弧上两个地点的数据。此处不包括斯科舍板块的北方边缘，因为极地计划不涵盖该地区。另一项提案将要求支持重新测量南美洲的SCARP全球定位系统台站。关于南极半岛地区，在乔治王岛弗雷基地（1996年）和南奥克尼群岛阿根廷基地（1998年）建立了连续运行的全球定位系统台站。1997年在南极半岛区域建立了一些纪念性地点，以支持1997年12月和1998年12月的卫星式全球定位系统工作。由于预期布兰斯菲尔德海峡的地壳运动缓慢，而且最初的拨款已经到期，因此在足够的时间过去之前不会进行进一步的数据收集，以便新的测量可以预期产生精确的结果。这项工作的主要目的是完成量化与布兰斯菲尔德海峡、南设得兰群岛微板块、并识别GPS数据可能揭示的任何其他独立的构造块。在2002-2003年季节期间，将利用船舶支助完成这项合同规定的测量工作。这将是第一次测量后的五年，并将提供相当精确的水平速度。该项目将完成单一数据集的采集、处理和解释，以继续国家科学基金会资助的项目的初始阶段，测量沿着斯科舍板块南缘的地壳运动。来自德克萨斯大学的一名主要研究员和一名研究生将进行实地考察。来自夏威夷大学的一名研究生将处理与以前数据一致的新数据，所有SCARP调查人员（来自美国的Bevis，Dalmarty，Smalley，Taylor）都将处理这些数据。美国德州夏威夷和美国。孟菲斯）将参与解释数据。英国南极调查局（BAS）和阿尔弗雷德·韦格纳研究所（AWI）也认识到斯科舍板块和布兰斯菲尔德系统在全球和当地板块构造框架中的重要性。他们也使用全球定位系统测量该地区的地壳运动，并复制了我们的一些站点。他们比我们更早开始，最近才开始收集数据，大概会继续收集数据，他们已经发表了一些结果。SCARP，BAS和AWI之间的合作已经开始，将继续进行这项新的工作。预计将联合和单独出版。现有的SCARP网络有几个优点，证明收集和分析另一组数据是合理的。一个是SCARP已经在史密斯岛、洛岛和利文斯顿岛建立并测量了GPS站点，而其他组织还没有。这些地点大大扩展了南设得兰群岛微板块的范围，因此我们可以确定一个更精确的旋转极，并认识到南设得兰群岛弧内的任何子块。史密斯岛和洛岛靠近布兰斯菲尔德盆地的末端，在那里，南设得兰群岛微板块之间的相对运动必须以某种方式终止，也许是由于沿着希罗断裂带的延伸发生断层作用。另一个优点是，SCARP下的测量是使用固定高度的桅杆进行的，在精确地重新占据每个站点时，可以消除几乎一毫米的垂直误差。与冰后期反弹相关的垂直运动应该在几毫米/年的数量级上，这最终将是可测量的。在南设得兰群岛的一些弧形岛屿上出现的中全新世海岸线超过20米，这表明垂直运动是重要的。因此，这项工作将有助于了解板块运动和冰后反弹的冰质量损失在该地区。

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, provides funds and field support to continue a study of plate motions in the Antarctic Peninsula and Scotia Sea region. The principal aim of the original "Scotia Arc GPS Project (SCARP)" was to determine motions of the Scotia Plate relative to adjacent plates and to measure crustal deformation along its margins with special attention to the South Sandwich microplate and Bransfield Strait extension. The focus of the present proposal is confined to the part of the SCARP project that includes GPS sites at Elephant Island, the South Shetland Islands and on the Antarctic Peninsula. The British Antarctic Survey provides data from two sites on the Scotia arc for this project. The northern margin of the Scotia Plate is not included herein because that region is not covered under Polar Programs. A separate proposal will request support for re-measuring SCARP GPS stations in South America. With regard to the Antarctic Peninsula area, continuously operating GPS stations were established at Frei Base, King George Island (in 1996) and at the Argentine Base, South Orkney Islands (in 1998). A number of monumented sites were established in the Antarctic Peninsula region in 1997 to support campaign-style GPS work in December 1997 and December 1998. Because of the expected slow crustal motion in the Bransfield Strait and expiration of the initial grant, no further data collection will be done until enough time has passed so that new measurements can be expected to yield precise results.The primary aim of this work is to complete the measurements required to quantify crustal deformation related to opening of the Bransfield Strait, the South Shetland microplate, and to identify any other independent tectonic blocks that the GPS data may reveal. The measurements to be completed under this award will be done using ship support during the 2002-2003 season. This would be five years after the first measurements and would provide quite precise horizontal velocities. This project will complete the acquisition, processing, and interpretation of a single data set to continue this initial phase of the NSF-funded project to measure crustal motions along the southern margin of the Scotia plate. A principal investigator and one graduate student from the University of Texas will perform fieldwork. A graduate student from the University of Hawaii will process the new data consistent with previous data, and all of the SCARP investigators (Bevis, Dalziel, Smalley, Taylor: from U. Texas, U. Hawaii, and U. Memphis) will participate in interpreting the data. The British Antarctic Survey (BAS) and Alfred Wegener Institute (AWI) also recognized the importance of the Scotia plate and the Bransfield system in both global and local plate tectonic frameworks. They, too, have used GPS to measure crustal motions in this region and duplicate a number of our sites. They began earlier than we, have taken data more recently, presumably will continue taking data, and they have published some results. The collaboration between SCARP, BAS, and AWI begun earlier, will continue into this new work. Joint and separate publications are anticipated. The existing SCARP network has several advantages that justify collection and analysis of another set of data. One is that SCARP has established and measured GPS sites on Smith, Low, and Livingston Islands, where other groups have not. These sites significantly extend the dimensions of the South Shetland microplate so that we can determine a more precise pole of rotation and recognize any sub-blocks within the South Shetland arc. Smith and Low Islands are near the end of the Bransfield Basin where relative motion between the South Shetland Microplate must somehow terminate, perhaps by faulting along an extension of the Hero fracture zone. Another advantage is that measurements under SCARP were made using fixed-height masts that eliminate all but a fraction of a millimeter of vertical error in exactly re-occupying each site. Vertical motion associated with postglacial rebound should be on the order of several mm/yr, which will eventually be measurable. Mid-Holocene shorelines that emerged to more than 20m on some South Shetland arc islands suggest that vertical motion is significant. Thus, this work will contribute to understanding both plate motions and post-glacial rebound from ice mass loss in the region.