Tectonic Summary

The April 3, 2014, M 7.7 earthquake off the west coast of northern Chile occurred as the result of thrust faulting at shallow depths, approximately 23 km south of the city of Iquique. At the location of the event, the Nazca plate subducts eastward beneath the South America plate at a velocity of about 73 mm/yr. The location and mechanism of the earthquake are consistent with slip on the plate boundary interface, or megathrust, between these two major plates. Subduction along the Peru-Chile Trench to the west of Chile has led to uplift of the Andes Mountain Range and has produced some of the largest earthquakes in the world, including the damaging M 8.8 Maule earthquake in central Chile in 2010, and the largest earthquake on record, the M 9.5 earthquake in southern Chile in 1960.

The April 3rd earthquake is an aftershock of the M 8.2 Iquique earthquake that occurred on April 1, 2014, approximately 110 km to the north of the April 3rd event. The M 8.2 event triggered a tsunami with measured heights near 2 m along the northern Chile and southern Peru coasts. Since the M 8.2 event, 47 aftershocks ranging from M 4.2 to this M 7.7 event have occurred, including a M 6.4 earthquake on April 2. The current seismic sequence was preceded by a foreshock sequence that began on March 16, 2014, with a M 6.7 earthquake close to the epicenter of the April 1st M 8.2 event.

This segment of the subduction zone, known as the Iquique or northern Chile seismic gap, last ruptured during an earthquake of about M 8.8 in 1877. Other recent large plate boundary ruptures bound this seismic gap, including the 2001 M 8.4 Peru earthquake adjacent to the south coast of Peru to the north, and the 2007 M 7.7 Tocopilla, Chile, and 1995 M 8.1 Antofagasta, Chile, earthquakes to the south.

While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Thrust-faulting events of the size of the April 3, 2014, earthquake are typically about 100x50 km (length x width); modeling of this earthquake implies dimensions of about 70x60 km, predominantly down-dip of the hypocenter, and immediately south of the M 8.2 rupture 2 days earlier. These two ruptures have not filled the seismic gap; a substantial section remains unruptured, particularly to the south of the April 3rd event.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)

Event Details

Event Map

Tectonic Summary

Historical Magnitude 4.5+ (100km)

Tectonic Summary

Historical Magnitude 4.5+ (100km)