NazcaPlate

The Nazca tectonic plate is west of the South American Plate that covers, of course, South America. It has a convergent boundary with that plate. Now, a convergent boundary is when one tectonic plate's border goes under that of the other. It's southern border is divergent, or moves apart from, with the Antarctic Plate. It borders with the Pacific Plate at another divergent boundary. The north side is yet another divergent boundary with the Cocos Plate. It moves east 3.7 centimeters a year! The June 20 earthquake occurred within the Nazca plate along the west coast of South America. The Nazca plate is seismically active down to depths of about 170 km! The largest earthquake known to have occurred in the subducted Nazca plate was the Bolivian earthquake of June 19, 1994, which had a magnitude of 8.2. Colton- It is named after the Nazca region of southern Peru. Sources;
 * http://en.wikipedia.org/wiki/Nazca_Plate
 * http://neic.usgs.gov/neis/eq_depot/2003/eq_030620_06/