Collaborative Research: A Broadband Seismic Investigation of Deep Continental Structure Across the East-West Antarctic Boundary

该奖项由极地方案办公室南极地质和地球物理方案提供，支持一个通过调查南极东西边界下的地壳和上地幔结构来评估南极构造发展的地球动力学模型的项目。这项实验将使用集中的宽带地震仪部署来解决与南极大陆构造发展有关的两个突出问题。(1)横贯北极山脉的起源。尽管横贯北极山脉被广泛认为是裂谷侧翼隆升的经典例子，但对于确切的隆升机制似乎没有达成多少共识。人们提出了许多机制，从延迟相变到转换侧向隆升，所有这些机制都对山前裂谷侧下方和邻近的上地幔结构做出了各种假设。(2)东南极克拉通的结构。经冰川负荷校正后，东南极显示出任何主要克拉通地块中最高的模式高程。南极东部的异常高程可能是大陆冰川开始的一个重要因素。然而，这种异常地形的支撑机制尚不清楚；可能的模式包括：(A)增厚的地壳的均衡抬升，(B)异常亏损的上地幔，和(C)热修改的上地幔，以及动态抬升。古老的大陆岩石圈的横向范围也是不确定的。特别是，旧岩石圈是否在罗斯造山运动期间变形的地壳岩石下延伸到东南极西部边缘尚不清楚。为了研究横跨南极东西边界的地壳和上地幔结构的细节，本次被动地震实验由三部分组成：(1)由17个宽带地震台组成的1400千米长的线性阵列，从南极东部克拉通的高中心区延伸到横贯南极的山脉(阵列1)。(2)由16个宽带地震台组成的400公里的交叉线性阵列(阵列2)。该阵列由16个宽带地震台从海岸延伸穿过干旱山谷地区的山脉，几乎垂直于山脉的走向。(3)罗斯岛和Terra Nova Bay周围沿海地区的11个宽带台站的阵列(阵列3)。这项实验将在三年内进行，以便从自然发生的地震中收集足够的数据，并将于2000年11月开始。将完成地面高程和冰层厚度的航空测量，以支持这项工作。如果可行，还将收集航地力和航磁学数据。数据将使用各种经过验证的建模技术进行分析，包括体波和面波层析、接收器函数反演和横波分裂分析。这些分析的结果将是横跨南极东西边界的地壳厚度、上地幔结构、各向异性和地幔不连续地形图的变化。这些结果将为理解南极大陆的地球动力学提供坚实的基础。

9909603WiensThis award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a project to evaluate geodynamic models for the tectonic development of Antarctica by investigating crust and upper mantle structure beneath the East-West Antarctic boundary. This experiment will use a focused broadband seismograph deployment to address two outstanding problems concerning the tectonic development of the Antarctic continent. (1) The origin of the Transantarctic Mountains.Even though the Transantarctic Mountains are widely considered a classic example of rift flank uplift, there appears to be little consensus about the exact uplift mechanism. Many mechanisms have been proposed, ranging from delayed phase changes to transform-flank uplift, all of which make various assumptions about upper mantle structure beneath and adjacent to the rift-side of the mountain front. (2) The structure of the East Antarctic Craton.East Antarctica displays the greatest modal elevation of any major cratonic block when corrected for glacial loading. The anomalous elevation of East Antarctica may have been an important factor in the onset of continental glaciation. However, the support mechanism for this anomalous topography is unknown; possible models include isostatic uplift from (a) thickened crust, (b) anomalously depleted upper mantle, and (c) thermally modified upper mantle, as well as dynamic uplift. The lateral extent of the very old continental lithosphere is also uncertain. In particular, it is unknown whether the old lithosphere extends to the western edge of East Antarctica beneath the crustal rocks deformed during the Ross Orogeny.To examine details of the crust and upper mantle structure across the East-West Antarctic boundary, this passive seismic experiment is comprised of three elements:(1) A 1400 km linear array of 17 broadband seismic stations extending from the high central regions of the East Antarctic craton to the Transantarctic Mountains (Array 1).(2) An intersecting 400 km linear array of 16 broadband seismic stations extending from the coast across the Transantarctic mountains nearly perpendicular to the strike of the range in the dry valleys region (Array 2).(3) An array of 11 broadband stations in coastal regions around Ross Island and Terra Nova Bay (Array 3).This experiment will be conducted over a three-year period, to allow sufficient data collection from naturally occurring earthquakes, and will begin in November 2000. Airborne surveys for surface elevation and ice thickness will be completed in support of this work. If feasible, aerogravity and aeromagnetics data will also be collected. Data will be analyzed using a variety of proven modeling techniques, including body and surface wave tomography, receiver function inversion, and shear wave splitting analysis. The results of these analyses will be maps of the variation in crustal thickness, upper mantle structure, anisotropy, and mantle discontinuity topography across the boundary of East and West Antarctica. These results will provide a solid foundation for understanding the geodynamics of the Antarctic continent.