A Broadband Seismic Experiment for Study of the Tectonics and Structure of the Antarctic Peninsula and Scotia Sea Regions

维恩斯和赵OPP 9527366摘要南极半岛和斯科舍板块地区的现今构造和地震结构是世界上最不了解的地区之一。该地区提供了独特而复杂的地球动力学环境，如最近沿南设得兰海沟火山活动的停止和布兰斯菲尔德海峡火山活动和裂谷的开始，德雷克海峡地区可能存在扩散变形和/或微板块，以及南三明治弧后的快速弧后扩张。该奖项支持美国参与研究南极半岛和斯科舍海地区地震构造和地震结构的国际努力，该努力从1996-1997年野外季节开始大规模部署宽带地震仪。该项目将在南极半岛地区、智利最南端和南乔治亚岛部署9台宽带PASSCAL地震仪，为期2年。以下问题将被讨论：1)是否有地震学证据，无论是俯冲带地震或地震结构的形式，目前俯冲到南极半岛以下？2)是否有证据表明，大规模地幔流动南美洲进入南大西洋？3)区域地震和震源机制是否与目前的Scotia板块运动学模型一致，这意味着德雷克海峡地区的挤压变形？4)南三明治俯冲带的深部结构？5)布兰斯菲尔德海峡和南三明治地区活动的弧后扩张中心的地震结构是什么？回答这些问题将有助于约束重要的构造问题，如板块运动变化的原因，什么过程引发弧后扩张，以及地幔流动与地表构造的关系。

Wiens and Zhao OPP 9527366 Abstract The present day tectonics and seismological structure of the Antarctic Peninsula and Scotia plate region are among the most poorly understood of any location in the world. This region offers a unique and complex geodynamic setting, as illustrated by the recent cessation of volcanism along the South Shetland Trench and onset of volcanism and rifting in the Bransfield Strait, the possible presence of diffuse deformation and/or microplates in the Drake Passage region, and fast back-arc spreading behind the South Sandwich Arc. This award supports the US component of an international effort to study the seismotectonics and seismic structure of the Antarctic Peninsula and Scotia Sea regions using a large scale deployment of broad band seismographs beginning during the 1996- 1997 field season. The project will deploy 9 broadband PASSCAL seismographs for 2 years in the Antarctic Peninsula region, Southernmost Chile, and South Georgia Island. The following questions will be addressed: 1) Is there seismological evidence, in the form of either subduction zone earthquakes or seismic structure, for current subduction beneath the Antarctic Peninsula? 2) Is there evidence from seismic anisotropy for large scale mantle flow around South America into the South Atlantic? 3) Are regional earthquakes and focal mechanisms consistent with current kinematic models for the Scotia plate, which imply compressional deformation in the Drake Passage region? 4) What is the deep structure of the South Sandwich subduction zone? 5) What is the seismological structure of active back-arc spreading centers in the Bransfield Strait and South Sandwich regions? Answering these questions will help to constrain important tectonic questions such as the cause of plate motion changes, what processes initiate back arc spreading, and the relationship between mantle flow and surface tectonics.