East Antarctic intraplate earthquakes recorded by the AGAP/GAMSEIS temporary seismic array delineate possible ancient rift

East Antarctica is primarily a stable craton and thus little deformation as is seen in geodetic observations. Although Antarctica was once thought to be aseismic, small events have been detected teleseismically. In 2009 the AGAP/GAMSEIS project operated a network of 26 broadband seismic stations that recorded 27 seismic events (ML 1.74-3.43) The majority of events are 10-30 km deep indicating a tecontic origin. Most events occur beneath subglacial topographic depressions that border the Gamburtsev Subglacial Mountains (GSM). 16 events follow a linear chain of depressions between the GSM and the Vostok Subglacial Highlands (VSH) that link the Polar Subglacial Basin to the Lambert Graben. This particular feature was identified as an ancient 'rift' by Ferraccioli et al. (2011). Gravity data in the 'rift' is distinct from surrounding areas with high Bouger and low free air gravity anomalies in the 'rift', in contrast to the GSM and VSH (Ferraccioli et al., 2011). The `rift' is embedded in the seismically fast East Antarctic cratonic mantle (Heeszel et al., 2013), but it shows a narrow region of lower velocities (Lloyd et al., 2013) and has thinner continental crust (Hansen et al., 2010) than surrounding regions. The feature potentially represents a terrain boundary between the Mawson and Crohn cratons (Boger, 2011) or could be a failed continental rift. One year of data cannot fully constrain the underlying cause of the seismicity. To further characterize the tectonics we calculate first motion double couple focal mechanisms for events showing impulsive body wave arrivals and good azimuthal station coverage. Preliminary results show the majority of fault plane solutions are extensional with fault planes that orient parallel or subparallel to the strike of the 'rift'. We compute synthetic waveforms to further test the robustness of our fault plane solutions. We propose the events are intraplate earthquakes located in zones of weakness associated with a failed continental rifting episode, possibly along an ancient terrain boundary suture.