Seismic Swarm S20140305.2 Offshore Valparaíso, Chile

The seismic swarm designated S20140305.2 occurred offshore Valparaíso, Chile, from 10:51 on 4 March 2014 to 13:01 on 5 March 2014. Over 26 hours and 10 minutes, 25 earthquakes were recorded in this tectonically active segment of the Peru-Chile subduction zone.

This region lies where the Nazca Plate subducts beneath the South American Plate at a convergence rate of approximately 6.6 centimeters per year. The resulting megathrust interface generates frequent seismic activity, including both large earthquakes and episodic swarms. Depths of events in the swarm ranged from 6 km to 47 km, consistent with activity along the plate interface and within the overriding crust.

The swarm began with two moderate events exceeding magnitude 5.0, followed by a sequence of smaller shocks. Magnitudes decreased progressively, with the majority falling between 2.4 and 3.6. Such patterns are characteristic of swarm sequences in subduction settings, where fluid migration or aseismic slip can trigger distributed seismicity without a single dominant mainshock.

Chile’s central coast has a well-documented history of great earthquakes. The 2010 Maule event (Mw 8.8) ruptured a segment immediately south of Valparaíso, producing widespread aftershock activity that continued for years. Historical records indicate three swarms in the broader offshore Valparaíso area since 2000, with the earliest occurring in 2010. These episodes highlight the persistent stress accumulation and release along this portion of the margin.

The 2014 swarm did not produce reported damage or tsunami effects, reflecting the moderate energy release and offshore location. Continued monitoring of such sequences contributes to improved understanding of precursory behavior ahead of potentially larger ruptures in this high-hazard zone.

References

SeismoSight internal swarm classification S20140305.2 USGS Earthquake Catalog (regional tectonics) Chilean National Seismological Center historical records