Buried deep beneath the Antarctic polar ice sheet, the geological structure and tectonic activity of East Antarctica have long remained unknown. The apparent lack of tectonic seismicity was thought to be anomalous relative to other continental interiors and has been attributed to a lack of intraplate stress due to the surrounding spreading ridges and low absolute plate velocity or to the weight of ice sheets increasing the normal stress. Here we report 27 intraplate tectonic earthquakes detected by the AGAP/GAMSEIS seismic array during 2009 in the interior of East Antarctica, which represents locally recorded seismicity in the region. The earthquakes are primarily extensional and located at shallow to mid-crustal depths beneath sedimentary basins aligned linearly adjacent to the Gamburtsev Subglacial Mountains. The basins may be part of an ancient continental rift system, which provides a zone of pre-existing tectonic weakness that focuses the seismicity. These events, when combined with events in published catalogues of Antarctic seismicity, indicate levels of seismicity in East Antarctica of the same order of magnitude as that of other stable cratons, such as the Canadian Shield.
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We thank the polar support specialists at IRIS/PASSCAL, who provided both instrumentation and field support during the operation of this array, and the pilots and staff of Kenn Borek Air and the New York Air National Guard for flight support. We thank the US Antarctic program, its contractors and staff at the South Pole Station, McMurdo Station and AGAP-S camp for logistical support. We also thank the members of the AGAP/GAMSEIS field team, particularly P. Shore, who were essential for gathering this data set. This research was supported by the US National Science Foundation under grants ANT-0537597, ANT-0537371, ANT-0838934, ANT-0838973 and PLR-1246712. Seismic data are available through the IRIS DMC. The facilities of the IRIS Consortium are supported by the NSF under Cooperative Agreement EAR-1063471, the NSF Office of Polar Programs and the DOE National Nuclear Security Administration.
The authors declare no competing interests.
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Lough, A.C., Wiens, D.A. & Nyblade, A. Reactivation of ancient Antarctic rift zones by intraplate seismicity. Nature Geosci 11, 515–519 (2018). https://doi.org/10.1038/s41561-018-0140-6
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