March 11, 2010 Earthquake: Rancagua, Chile

Felt Reports

Some damage (VII) at Rancagua. Felt (VI) at Curico, Santiago, San Vicente and Talca; (V) at Buin, Calera, Chillan, Colina, Concepcion, Melipilla, San Antonio, San

Fernando and Valparaiso; (IV) at Angol, Limache, Los Andes, Penaflor, Petorca, Puente Alto, Quillota, Quilpue, San Bernardo, Temuco, Villa Alemana and Vina del Mar. Felt in much of central and southern Chile as far as La Serena and Coihaique. Felt (V) at San Rafael, (IV) at Cordoba, (III) at Mendoza and (II) at Buenos Aires, Argentina. Felt at Montevideo, Uruguay and (II) at Asuncion, Paraguay. A small tsunami was recorded with wave heights (peak-to-trough) of 29 cm at San Antonio and 16 cm at Valparaiso.

Tectonic Summary

The Chile earthquakes of March 11, 2010, 14:39 UTC and 14:55 UTC, occurred in the region of the plate boundary between the Nazca and South America plates, in the aftershock region of the great Chile earthquake of February 27, 2010. The March 11 earthquakes almost certainly occurred as the result of the change of regional stress caused by the February 27 earthquake. Preliminary analyses of their locations and seismic-wave radiation patterns, however, imply that the March 11 shocks occurred as the result of normal faulting within the subducting Nazca plate or the overriding South America plate, unlike the February 27 earthquake, which occurred as thrust faulting on the interface between the two plates. At present, the focal depths of the shocks are not known with sufficient precision to confidently determine within which of the Nazca or South America plate the earthquakes occurred.

(above from reference #1053)