April 3, 2014 Earthquake: Iquique, Northern, Chile

Felt (VIII) at Alto Hospicio, Arica, Cuya, Iquique and Pisagua; (VII) at Quillagua, Sierra Gorda and Tocopilla; (VI) at Calama, Oficina Maria Elena and Mejillones; (V) at Alcerreca and Antofagasta. Felt (IV) at Arequipa, Peru. Also felt at Pacocha. Felt at La Paz, Bolivia.

Tectonic Summary

The April 3, 2014 M 7.6 earthquake off the west coast of northern Chile occurred as a result of thrust motion at a depth of approximately 40 km, 23 km south of the city Iquique. The location and mechanism of the earthquake are consistent with slip on the plate boundary interface, or megathrust, between the Nazca and South America plates. At the latitude of the event, the Nazca plate is subducting beneath South America at a rate of ~73 mm/yr.

This earthquake is an aftershock of the M 8.2 subduction zone earthquake that occurred April 1, 2014. The M 8.2 event triggered a tsunami with measured heights near 2 meters along the northern Chile and southern Peru coasts. Since the M8.2 event, 47 aftershocks ranging from M 4.2 to this M 7.8 event have occurred, including a M 6.4 on April 2. The current seismic sequence was preceeded by a foreshock sequence that began on March 16, 2014, with a M 6.7 earthquake close to the epicenter of the April 1 M 8.2 event. This segment of the subduction zone, known as the Iquique or Northern Chile seismic gap, last ruptured during the 1877 M8.8 Iquique earthquake. Other recent large plate boundary ruptures bound the possible rupture area of the April 1 event, 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.

(above from reference #1053)