The 2013 M7.7 Scotia Sea Earthquake: Tectonic Setting and Regional History

The Scotia Sea, located in the Southern Ocean between the southern tip of South America and the Antarctic Peninsula, forms a tectonically dynamic marine basin. It is underlain primarily by the Scotia Plate, a small, independently moving fragment of oceanic lithosphere bounded by the South American Plate to the north and the Antarctic Plate to the south. This plate configuration results from the long-term fragmentation of the supercontinent Gondwana, which began in the Mesozoic era and led to the opening of the Drake Passage approximately 30–40 million years ago. The passage facilitated the establishment of the Antarctic Circumpolar Current, influencing global climate patterns.

The Scotia Plate interacts with neighboring plates along a series of transform faults, spreading centers, and subduction zones. To the east, the South Sandwich subduction zone marks the descent of South American Plate crust beneath the Sandwich Plate, generating frequent seismic activity. The western and northern margins feature strike-slip faulting along the Shackleton Fracture Zone and North Scotia Ridge. These boundaries accommodate relative plate motions of several centimeters per year, contributing to the region’s elevated seismicity.

On 17 November 2013 at 09:04 UTC, a magnitude 7.7 earthquake struck the Scotia Sea at a focal depth of 10.0 km. This event represents the sole M7+ earthquake recorded in the region since 1 January 2000. Its shallow depth and location within the Scotia Plate interior or along a nearby transform boundary are consistent with the area’s tectonic regime, where strike-slip mechanisms predominate. No significant aftershock sequence or tsunami was widely reported, reflecting the event’s offshore setting and moderate energy release relative to subduction-zone megathrusts.

Historically, the Scotia Sea has experienced recurrent moderate-to-large earthquakes due to its position at the nexus of multiple plate boundaries. Paleoseismic and geodetic studies indicate that the Scotia Plate has undergone gradual eastward migration since the Eocene, driven by the ongoing separation of South America and Antarctica. This motion sustains transform faulting and occasional intraplate deformation, as exemplified by the 2013 event.

Seismic monitoring by global networks confirms that the Scotia Sea remains an active but not hyperactive seismic province compared with major subduction zones. Continued plate motion suggests the potential for future events of similar magnitude along the region’s fault systems.

References

• United States Geological Survey Earthquake Catalog (event data for 17 November 2013 Scotia Sea earthquake).
• Bird, P. (2003). An updated digital model of plate boundaries. Geochemistry, Geophysics, Geosystems.
• Barker, P. F. (2001). Scotia Sea tectonic evolution: Recent refinements. Geological Society Special Publications.