The 2011 Carahue Earthquake: Seismicity in Southern Chile

A magnitude 7.2 earthquake struck 42 km NNW of Carahue, Chile, at 20:20 local time on 2 January 2011. The event occurred at a focal depth of 24 km. This earthquake took place within the Araucanía Region of southern Chile, an area characterized by intense seismic activity due to its position along the convergent boundary between the Nazca and South American tectonic plates.

Southern Chile lies within the Andean subduction zone, where the oceanic Nazca Plate descends beneath the continental South American Plate at a rate of approximately 6–7 cm per year. This tectonic setting produces frequent megathrust earthquakes along the plate interface, as well as intraslab events within the subducting slab. The 24 km depth of the 2011 event is consistent with rupture near the seismogenic interface. The Araucanía Region has experienced recurrent large earthquakes throughout recorded history, including the 1960 Valdivia earthquake (Mw 9.5), the largest instrumentally recorded event worldwide, and the 2010 Maule earthquake (Mw 8.8), whose rupture zone extended into nearby coastal areas.

Seismic monitoring indicates that strong earthquakes (M ≥ 7.0) have been relatively infrequent in the immediate vicinity since 2000, with the 2011 Carahue event standing as a notable occurrence. The region’s geology features the Coastal Range and Central Valley, underlain by accreted terranes and volcanic arcs influenced by ongoing subduction. Historical records document major events in 1575, 1737, and 1837, underscoring a pattern of strain accumulation and release along the megathrust.

Post-event analysis showed limited surface rupture, typical for moderate-depth interface earthquakes in this setting. The 2011 event contributed to ongoing studies of aftershock sequences and stress transfer following the 2010 Maule rupture. Updated seismic hazard assessments for southern Chile continue to emphasize the potential for future large events given the locked segments of the plate boundary.

References

• United States Geological Survey Earthquake Catalog
• Servicio Nacional de Geología y Minería (SERNAGEOMIN) seismic reports
• Tectonic summaries from the International Seismological Centre