The Mw 7.7 Nasca (Peru) Earthquake, November 12, 1996: A Repetition of the 1942 Event?

MAIN EVENT At 16:59 on 12 November 1996 (UT) a Mw 7.7 earthquake occurred off the coast of Southern Peru, along the contact zone between the subducting Nazca Plate and the upper South American plate. Three locations are available for this event (Figure 1): (1) the PDE located this event at 14.99°S, 75.68°W, with a “normal” 33 km depth (PDE, 1997), (2) the centroid location: 15.09°S, 75.37°W, depth 37.0 km (PDE, 1997), and (3) the location obtained with the local permanent Peruvian network run by the Instituto Geofisico del Peru (IGP): 15.30°S, 76.04°W, depth 14 km. In the following discussion we use the PDE location. The Harvard University centroid-moment tensor solution (Figure 1) shows that this event was due to slip of the downgoing Nazca plate under the South American plate. This is a complex event, with at least two larger events occurring about 20 and 33 seconds after the...