Geodetic, teleseismic, and strong motion constraints on slip from recent southern Peru subduction zone earthquakes
We use seismic and geodetic data both jointly and separately to constrain coseismic slip from the 12 November 1996 M_w 7.7 and 23 June 2001 M_w 8.5 southern Peru subduction zone earthquakes, as well as two large aftershocks following the 2001 earthquake on 26 June and 7 July 2001. We use all available data in our inversions: GPS, interferometric synthetic aperture radar (InSAR) from the ERS-1, ERS-2, JERS, and RADARSAT-1 satellites, and seismic data from teleseismic and strong motion stations. Our two-dimensional slip models derived from only teleseismic body waves from South American subduction zone earthquakes with M_w > 7.5 do not reliably predict available geodetic data. In particular, we find significant differences in the distribution of slip for the 2001 earthquake from models that use only seismic (teleseismic and two strong motion stations) or geodetic (InSAR and GPS) data. The differences might be related to postseismic deformation or, more likely, the different sensitivities of the teleseismic and geodetic data to coseismic rupture properties. The earthquakes studied here follow the pattern of earthquake directivity along the coast of western South America, north of 5°S, earthquakes rupture to the north; south of about 12°S, directivity is southerly; and in between, earthquakes are bilateral. The predicted deformation at the Arequipa GPS station from the seismic-only slip model for the 7 July 2001 aftershock is not consistent with significant preseismic motion.
Additional Information© 2007 American Geophysical Union. Received 17 January 2006; revised 12 September 2006; accepted 18 October 2006; published 17 March 2007. We thank H. Nakagawa for assistance in processing the JERS data; E. Fielding, E. Price, V. Wolf, and G. Peltzer for helping us find and process the RADARSAT data; T. Melbourne for his processed Arequipa GPS data; M. Giovanni for the relocated aftershocks for the 2001 earthquake; and A. Rodriguez-Marek, J.-P. Ampuero, and R. Allmendinger for discussions. P. Lundgren and Associate Editor S. Cohen provided helpful critical reviews. This study used ERS SAR imagery acquired under a category 1 research project from the European Space Agency. JERS SAR data were provided by the Remote Sensing Technology Center of Japan through research user PAR. RADARSAT SAR data were provided by the Alaska SAR Facility. The GMT program [Wessel and Smith, 1998] was used to create several figures. T.H.D. and E.O.N. acknowledge support of NSF grant EAR 0003621; and M.E.P.'s contribution was funded by NSF grant EAR 0510719.
Published - Pritchard_JGR2007.pdf