Surface Deformation Associated with the Mw 6.4, 24 February 2004 Al Hoceima, Morocco, Earthquake Deduced from InSAR: Implications for the Active Tectonics along North Africa

Abstract

We study the surface deformation associated with the 24 February 2004 Al Hoceima earthquake (Mw 6.4) that recently affected the Rif Mountains of Mo- rocco. The coseismic displacement field is mapped using synthetic aperture radar interferometry (InSAR) with the Envisat (ESA) satellite data acquired in the ascend- ing and descending modes. Our analysis and modeling of InSAR data suggest that the earthquake is associated with a northwest-southeast-trending right-lateral, ap- parently blind strike-slip fault with a seismic moment reaching 6.8 10 18 N m. This result is in contrast with the north-northeast-south-southwest left-lateral fault mech- anism inferred from the modeling of seismic waves. Thrust-and-fold structures of the Rif Mountains developed during the Tertiary period, but the recent significant seismic events and late-Quaternary deformation indicate east-west extension accom- modated by north-south-trending normal and northwest-southeast- and northeast- southwest-trending conjugate strike-slip faults. The active deformation illustrates the fragmentation of the Rif Mountain range due to the Africa-Iberia collision and west- southwestward escape tectonics.