Geophys. J. Int. (2006) 166, 1347–1362 doi: 10.1111/j.1365-246X.2006.03071.x Fault identification for buried strike-slip earthquakes using InSAR: The 1994 and 2004 Al Hoceima, Morocco earthquakes Juliet Biggs,1 Eric Bergman,2 Brian Emmerson,3 Gareth J. Funning,4 James Jackson,3 Barry Parsons1 and Tim J. Wright1 1COMET, Department of Earth Sciences, University of Oxford. E-mail:
[email protected] 2CIEI, Department of Physics, University of Colorado, Boulder, Colorado, 80309, USA 3COMET, Bullard Laboratories, Department of Earth Sciences, University of Cambridge 4Berkeley Seismological Laboratory, University of California, Berkeley, California, USA Accepted 2006 May 15. Received 2006 May 15; in original form 2005 September 15 SUMMARY The 1994 M w 6.0 and 2004 M w 6.5 Al Hoceima earthquakes are the largest to have occurred in Morocco for 100 yr, and give valuable insight into the poorly understood tectonics of the area. Bodywave modelling indicates the earthquakes occurred on near-vertical, strike-slip faults with the nodal planes oriented NW–SE and NE–SW. Distinguishing between the primary fault plane and auxiliary planes, using either geodetic or seismic data, is difficult due to the spatial symmetry in deformation fields and radiation pattern of moderately sized, buried, strike- slip earthquakes. Preliminary studies, using aftershock locations and surface observations, have been unable to identify the orientation of the primary fault plane for either earthquake conclusively. We use radar interferometry and aftershock relocation of the earthquake sequence to resolve the ambiguity. For the 2004 earthquake, inverting the interferograms for a uniform slip model based either of the two potential nodal planes results in similar misfits to the data.