Tectonic Summary

The November 28th, 2021, M 7.5 northern Peru earthquake occurred as the result of normal faulting at an intermediate depth, approximately 110 km beneath the Earth's surface within the subducted lithosphere of the Nazca plate. Focal mechanism solutions indicate that rupture occurred on either a north-northwest or south-southeast striking, moderately dipping normal fault. At the location of the earthquake, the Nazca plate moves to the east relative to the South America plate at a velocity of about 70 mm/yr, subducting at the Peru-Chile Trench, to the west of the Peruvian coast and the November 28th earthquake. Earthquakes of northern Peru and most of western South America are due to strains generated by this ongoing subduction; at this latitude, the Nazca plate is seismically active to depths of about 650 km. This earthquake occurred in a segment of the subducted plate that has produced frequent earthquakes with focal depths of 100 to 150 km.

Earthquakes like this event, with focal depths between 70 and 300 km, are commonly termed “intermediate-depth” earthquakes. Intermediate-depth earthquakes represent deformation within subducted slabs rather than at the shallow plate interface between subducting and overriding tectonic plates. They typically cause less damage on the ground surface above their foci than is the case with similar-magnitude shallow-focus earthquakes, but large intermediate-depth earthquakes may be felt at great distance from their epicenters.

Large intermediate-depth earthquakes are reasonably common in this section of the Nazca slab, and five other intermediate-depth M 7+ events have occurred within 250 km of the November 28th earthquake over the past century. A M 7.5 earthquake on September 26th 2005, located at a similar depth but approximately 140 km to the south of the November 28th, 2021 earthquake, caused 5 deaths, about 70 injuries, and significant damage in the surrounding region. More recently, an M8.0 earthquake on May 26th 2019, approximately 230 km to the southeast of the November 28th 2021 earthquake, resulted in 2 deaths.

Event Details

Event Map

Tectonic Summary

Historical Magnitude 4.5+ (100km)

Tectonic Summary

Historical Magnitude 4.5+ (100km)