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

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，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洲构造发展的地球动力学模型的项目。本次实验将使用集中的宽带地震仪部署，以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升的典型例子，但对于确切的隆升机制似乎鲜有共识。人们提出了许多机制，从延迟相位变化到转换翼侧隆起，所有这些机制都对山前裂谷下方和附近的上地幔结构做出了各种假设。(2)东南极克拉通构造。在对冰川负荷进行校正后，东南极洲是所有主要克拉通块体中模态海拔最高的。东南极洲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尚不清楚；可能的模式包括：(a)地壳增厚，(b)上地幔异常枯竭，(c)上地幔热改造，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。特别是，旧岩石圈是否延伸到东南极洲的西部边缘，在罗斯造山运动期间变形的地壳岩石下，这是未知的。为了研究横跨南极东西边界的地壳和上地幔结构的细节，该被动地震实验由三个要素组成：(1)由17个宽带地震台站组成的1400公里线性阵列，从东南极克拉通的高中心区域延伸至横贯南极山脉（阵列1）；(2)由16个宽带地震台站组成的400公里相交线性阵列，从海岸延伸至横贯南极山脉，几乎垂直于干谷地区的走向（阵列2）；(3)由11个宽带台站组成的沿海阵列罗斯岛和特拉诺瓦湾附近地区（阵列3）。这项实验将在2000年11月开始，为期三年，以便从自然发生的地震中收集足够的数据。为了支持这项工作，将完成地面高程和冰层厚度的航空测量。如果可行，还将收集航空重力和航空磁学数据。数据将使用各种成熟的建模技术进行分析，包括体波和面波断层扫描、接收函数反演和横波分裂分析。这些分析的结果将绘制出横跨东、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.