Results of seismic monitoring surveys of Deception Island volcano, Antarctica, from 1999-2011

Deception Island volcano (South Shetland Islands, Antarctica) has been monitored in summer surveys since 1994. We analyse the seismicity recorded from 1999-2011 with a local network and seismic arrays. It includes long-period (LP) events, volcanic tremor episodes and volcano-tectonic (VT) earthquakes. Long-period events are conspicuous, ranging from 58 (2007-08) to 2868 events (2003-04). The highest number of LP events in one day is 243 on 2 February 2001, and there are several discrete periods of intense LP activity. These variations may be related to alterations in the shallow hydrothermal system of Deception Island. The number of VT earthquakes recorded during the surveys range from 4 (2008-09) to 125 (2007-08). In some periods VT distributions are temporally and spatially homogeneous, with a generally low level of seismicity. In other periods we observe a peak of VT activity lasting a few days, concentrated in a particular area. These two patterns may respond to different processes, involving regional stresses and local tectonic destabilization induced by volcanic activity. Overall, this study indicates that over the period 1999-2011 the volcano presented a moderate level of seismicity, and suggests that there has been no significant reactivation of the volcano since the 1999 seismic crisis.