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

9909969 该奖项由极地方案办公室南极地质和地球物理方案提供，支持一个项目，通过调查南极东西边界下的地壳和上地幔结构，评估南极洲构造发展的地球动力学模型。这一实验将使用一个重点突出的宽带地震仪来解决有关南极大陆构造发展的两个突出问题。(1)横贯南极山脉的起源。尽管横贯南极山脉被广泛认为是裂谷侧翼隆起的典型例子，但对于确切的隆起机制似乎还没有达成共识。已经提出了许多机制，从延迟相变到转换侧翼隆起，所有这些机制都对山前裂谷侧下方和附近的上地幔结构做出了各种假设。 (2)东南极洲板块的结构。东南极洲板块在冰川负荷校正后显示出最大的模态海拔。 南极东部的异常海拔可能是大陆冰川作用开始的一个重要因素。 然而，这种异常地形的支撑机制是未知的;可能的模型包括均衡隆升（a）增厚的地壳，（B）异常亏损的上地幔，（c）热改造的上地幔，以及动力隆升。非常古老的大陆岩石圈的横向范围也不确定。 为了研究东南极大陆地壳和上地幔结构的细节，本次被动地震实验由三个部分组成：（1）17个宽频带地震台站组成的1400 km线性阵列，从东南极克拉通的高中心区延伸到横贯南极山脉（阵列1）。(2)由16个宽带地震台站组成的400公里交叉线性阵列，从海岸延伸到横贯南极山脉，几乎垂直于干谷地区山脉的走向（阵列2）。(3)在罗斯岛和特拉诺瓦湾周围沿海地区的11个宽带站阵列（阵列3），这项试验将在三年期间进行，以便能够从自然发生的地震中收集足够的数据，试验将于2000年11月开始。为支持这项工作，将完成地面高程和冰厚的航空测量。如果可行，还将收集航空重力和航空磁力数据。将使用各种经过验证的建模技术分析数据，包括体波和面波层析成像、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东南极洲和西南极洲边界的地壳厚度、上地幔结构、各向异性和地幔不连续地形的变化图。 这些结果将为了解南极大陆的地球动力学提供坚实的基础。

9909969 AnadakrishnanThis 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.