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

该奖项由极地项目办公室的南极地质和地球物理项目提供，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现场支持。最初的“斯科舍弧GPS项目”（SCARP）的主要目的是确定斯科舍板块相对于邻近板块的运动，并测量其边缘的地壳变形，特别关注南三明治微板块和布兰斯菲尔德海峡的延伸。本建议的重点限于SCARP项目的一部分，其中包括象岛、南设得兰群岛和南极半岛的GPS站点。英国南极调查局为这个项目提供了斯科舍弧线上两个地点的数据。斯科舍板块的北缘不包括在这里，因为该地区没有被极地计划所覆盖。另一项提案将要求支持在南美洲重新测量SCARP GPS站。关于南极半岛地区，在乔治国王岛的弗雷基地（1996年）和南奥克尼群岛的阿根廷基地（1998年）建立了持续运行的GPS站。1997年在南极半岛地区建立了一些纪念地，以支持1997年12月和1998年12月的运动式GPS工作。由于预计布兰斯菲尔德海峡的地壳运动缓慢，以及最初的拨款到期，在足够的时间过去之前，不会进行进一步的数据收集，以便新的测量可以产生精确的结果。这项工作的主要目的是完成所需的测量，以量化与布兰斯菲尔德海峡、南设得兰微板块开放有关的地壳变形，并确定GPS数据可能揭示的任何其他独立构造块。根据该合同，测量工作将在2002-2003年期间使用船舶支持完成。这将是第一次测量的五年后，将提供相当精确的水平速度。该项目将完成对单一数据集的采集、处理和解释，以继续美国国家科学基金会资助的测量斯科舍板块南缘地壳运动的项目的初始阶段。一名首席研究员和一名来自德克萨斯大学的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研究者（Bevis, Dalziel, Smalley， Taylor：来自U. Texas， U. Hawaii和U. Memphis）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体系在全球和本地板块构造框架中的重要性。他们也用GPS测量了这个地区的地壳运动，并复制了我们的一些站点。他们开始得比我们早，最近才开始收集数据，估计还会继续收集数据，他们已经公布了一些结果。早前开始的SCARP、BAS和AWI之间的合作将继续到这项新工作中。预期会有联合和单独的出版物。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微板块的尺寸，因此我们可以确定更精确的旋转极，并识别南设得兰弧内的任何子块。史密斯和洛岛靠近布兰斯菲尔德盆地的末端，在那里，南设得兰微板块之间的相对运动必须以某种方式终止，可能是通过沿Hero断裂带的延伸发生断裂。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地点时，除了一毫米的垂直误差外，消除了所有垂直误差。与冰期后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。在一些南设得兰岛弧上，出现了超过20米的中全新世海岸线，这表明垂直运动是显著的。因此，这项工作将有助于了解该地区的板块运动和冰块损失造成的冰川后反弹。

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.