Poster of the Northern Peru Earthquake of 24 August 2011 - Magnitude 7.0

Tectonic Summary

The August 24, 2011 M 7.0 Peru earthquake occurred at a depth of approximately 150 km beneath the Earths surface as a result of normal faulting within the subducting Nazca slab. The event struck near the boundary between the Nazca and South America plates, as the former sinks beneith the latter. At the location of this earthquake, the Nazca plate moves approximately east-northeast with respect to South America at a rate of 67 mm/yr. The Nazca plate is seismically active east-northeast of the August 24 epicenter to depths of over 600 km; the stresses generating this earthquake may result from the bending of the plate as it transitions from a sub-horizontal region west-southwest of the epicenter to sink at steeper dips towards the mantle transition zone.

The section of the subducting Nazca plate within 100 km of the epicenter of the August 24, 2011, earthquake has hosted moderate earthquakes in the past, with seven earthquakes of M 6 or greater in the past quarter century, though none have been as large as the August 24 event. The most recent nearby earthquake was a M 6.4 shock just over 10 km to the east in August 2008.

Earthquakes that have focal-depths between 70 and 300 km are commonly termed intermediate-depth earthquakes, as distinguished from shallow-focus earthquakes, having depths less than 70 km, and deep-focus earthquakes, having depths greater than 300 km. Intermediate-depth and deep-focus earthquakes represent deformation within subducted plates, rather than deformation at plate boundaries. Intermediate-depth and deep-focus earthquakes 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 and deep-focus earthquakes may be felt at great distances from their epicenters.

Earthquake Report

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