Seismic Structure of the Antarctic Upper Mantle Imaged with Adjoint Tomography
Seismic Structure of the Antarctic Upper Mantle Imaged with Adjoint Tomography
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DOI：
10.1029/2019jb017823
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发表时间：
2020-03
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通讯作者：
A. Lloyd;D. Wiens;H. Zhu;J. Tromp;A. Nyblade;R. Aster;S. Hansen;I. Dalziel;T. J. Wilson;E. Ivins;J. O’Donnell
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作者：
A. Lloyd;D. Wiens;H. Zhu;J. Tromp;A. Nyblade;R. Aster;S. Hansen;I. Dalziel;T. J. Wilson;E. Ivins;J. O’Donnell
南极洲和周围海洋下方的上地幔和过渡区是地球内部成像最差的区域之一。在过去15年中，部署了几个大型宽带区域地震台阵，并建立了新的常设地震台站。利用南极297个地震台站和40°S以南26个地震台站的地震资料，利用伴随层析成像技术，对上地幔及其过渡带的地震结构进行了成像。在20次迭代过程中，我们利用了包含P，S，Rayleigh和Love波的三分量地震图的相位观测，包括2001-2003年和2007-2016年发生的270次地震产生的反射和泛音。新的大陆尺度地震模型（ANT-20）具有60°S以南的区域尺度分辨率。在东南极洲，在德龙宁莫德地和恩德比-肯普地之下发现了较薄的大陆岩石圈。一个连续的慢波速度异常延伸从Balleny群岛通过西部罗斯湾和划定的新生代伸展和火山活动，跨越海洋和大陆地区的地区。慢波速度异常也在玛丽伯德地和沿着阿蒙森海岸下成像，延伸到南极半岛。这些异常仅限于地幔上部200-250 km，除了在玛丽伯德地附近，它们延伸到过渡带，并可能更深。最后，阿蒙森海岸的慢波速度沿着与离岸更深的异常联系在一起，表明可能与更深的地幔过程有关。
The upper mantle and transition zone beneath Antarctica and the surrounding oceans are among the poorest‐imaged regions of the Earth's interior. Over the last 15 years, several large broadband regional seismic arrays have been deployed, as have new permanent seismic stations. Using data from 297 Antarctic and 26 additional seismic stations south of ~40°S, we image the seismic structure of the upper mantle and transition zone using adjoint tomography. Over the course of 20 iterations, we utilize phase observations from three‐component seismograms containing P, S, Rayleigh, and Love waves, including reflections and overtones, generated by 270 earthquakes that occurred from 2001–2003 and 2007–2016. The new continental‐scale seismic model (ANT‐20) possesses regional‐scale resolution south of 60°S. In East Antarctica, thinner continental lithosphere is found beneath areas of Dronning Maud Land and Enderby‐Kemp Land. A continuous slow wave speed anomaly extends from the Balleny Islands through the western Ross Embayment and delineates areas of Cenozoic extension and volcanism that span both oceanic and continental regions. Slow wave speed anomalies are also imaged beneath Marie Byrd Land and along the Amundsen Sea Coast, extending to the Antarctic Peninsula. These anomalies are confined to the upper 200–250 km of the mantle, except in the vicinity of Marie Byrd Land where they extend into the transition zone and possibly deeper. Finally, slow wave speeds along the Amundsen Sea Coast link to deeper anomalies offshore, suggesting a possible connection with deeper mantle processes.