Seismic Swarm Activity in the South Sandwich Islands Region, December 2010

The South Sandwich Islands region lies within a tectonically active subduction zone in the southern Atlantic Ocean, where the South American Plate descends beneath the Scotia Plate along the South Sandwich Trench. This setting produces frequent seismic events, including earthquake swarms, due to ongoing plate convergence at rates of approximately 70–80 mm per year. The islands themselves form a volcanic arc resulting from this subduction, with associated volcanism and seismicity documented throughout the Holocene. Seismic swarms in this area often reflect stress adjustments along the plate interface or within the overriding plate, typically at depths between 10 and 40 km. Historical records indicate elevated activity linked to both interplate thrust faulting and intraslab events, consistent with the region's position on the Antarctic Plate boundary system. Updated global seismic catalogs confirm ongoing moderate-to-large earthquakes in the vicinity, underscoring the persistent hazard. Between 7 and 9 December 2010, a swarm comprising 10 earthquakes was recorded in the South Sandwich Islands region. The sequence began at 09:38 on 7 December with a magnitude 5.0 event at 40 km depth and concluded at 14:40 on 9 December. The largest event reached magnitude 6.3 at 29 km depth on 8 December. Other events included magnitudes ranging from 4.8 to 5.4, with depths varying from 10 to 32 km. Such swarms are characteristic of the region’s dynamic stress environment but do not necessarily precede a single mainshock. Since 2000, the area has experienced additional strong seismicity, including a magnitude 7.2 earthquake on 28 May 2016 located 83 km from the 2010 swarm center. This event further illustrates the subduction-driven seismicity that defines the South Sandwich Islands.

References

USGS Earthquake Catalog Global CMT Project NOAA National Centers for Environmental Information