Poster of the Maule, Chile Earthquake of 25 March 2012 - Magnitude 7.1

Tectonic Summary


Subduction zones such as the South America arc are geologically complex and generate numerous earthquakes from a variety of tectonic processes that cause deformation of the western edge of South America. Crustal deformation and subsequent mountain building in the overriding South America plate generate shallow earthquakes. Slip along the dipping interface between the two plates generates frequent and often large interplate earthquakes between depths of approximately 10 to 60 km. Since 1900, numerous magnitude 8 or greater earthquakes have occurred on the interface between the Nazca and South America plates, including the 1960 M9.5 earthquake in southern Chile, the largest instrumentally recorded earthquake in the world and the 2010 M8.8 earthquake north of the 1960 quake. Earthquakes can also be generated to depths greater than 600 km from internal deformation of the subducting Nazca plate. Although the rate of subduction varies little along the entire subduction zone, there are complex changes in geologic processes along the subduction zone that dramatically influence volcanic activity, earthquake generation and occurrence. For example, an extended zone of crustal seismicity in central-northern Argentina highlights a well-known 'flat-slab' region of this subduction zone, where the Nazca plate moves horizontally for several hundred kilometers before continuing its descent into the mantle. This transition in slab structure is coincident with a marked break in the Andes volcanic chain.

Earthquake Report


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