HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Full Text (PDF) Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Cakir, Z. Articles by Ait-Brahim, L. Search for Related Content GeoRef GeoRef Citation

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

¹ EOST—Institut de Physique du Globe
5, rue René Descartes
67084 Strasbourg Cedex, France
ziyadin.cakir{at}eost.u-strasbg.fr
 (Z.C., M.M., S.B.)

² Eurasian Institute of Earth Sciences ITU
Istanbul, Turkey
 (A.M.A.)

³ Laboratoire de Geophysique
CNRST
Rabat, Morocco
 (N.J.)

⁴ des Sciences de la Terre
Universite Mohammed V
Morocco
 (L.A.-B.)

View larger version (96K): [in a new window]   Figure 1. Al Hoceima region of Morocco with shaded relief (SRTM 90m). Large beach balls are focal-mechanism solutions of the 26 May 1994 and 24 February 2004 Al Hoceima earthquakes, whose epicenters are indicated by gray and black stars, respectively. Small black circles are M >4 aftershocks of the 2004 earthquake from Instituto Geografico Nacional (IGN) with focal-mechanism solutions from Stich et al. (2005). Dashed rectangles are the frames of the Envisat radar images with arrows showing the flight direction of the satellite that looks to the right. The convergent plate boundary between Africa and Eurasia is depicted with a thick gray line in the inset map with arrows illustrating the direction of convergence (DeMets et al., 1990; Nocquet and Calais, 2004).

View larger version (100K): [in a new window]   Figure 2. Tectonic map of the Al Hoceima region (compiled from Calvert et al., 1997; Ait Ibrahim, Tadili, et al., 2004) with surface cracks and fissures observed after the 2004 event (redrawn from Ait Brahim, Nakhcha, et al., 2004). Red circles are the M >4 aftershocks of the 2004 event whose epicenter is shown with a star (from IGN). Thick white line is the surface trace of the modeled fault plane.

View larger version (15K): [in a new window]   Figure 3. Baseline-time plot of the Envisat orbits used in this study. The elevation change that would produce an interferometric fringe (i.e., altitude of ambiguity), which depends on the interferometric baseline, is given in gray boxes. Interferograms shown in Figure 4 are produced using the interferometric pairs connected with bold lines.

View larger version (109K): [in a new window]   Figure 4. Coseismic Interferograms of the 24 February 2004 Al Hoceima earthquake. Each fringe shows 2.83 cm of surface displacement along the radar line of sight. Dashed lines are digitized fringes used in modeling the interferograms. Blue line is the best model fault. Barbed lines are inactive thrust faults shown to facilitate comparison of the interferograms. Black arrows indicate radar look direction.

View larger version (121K): [in a new window]   Figure 5. Synthetic interferograms obtained from joint inversion of ascending and descending data (digitized fringes, i.e., dashed lines) using modeled faults (black lines) with varying strike, dip, and mechanism (see Table 2 for details). (a) Planar and vertical fault with left-lateral slip. (b) Planar fault with 60° NW dip and left-lateral slip. (c) Curved fault with 70° NW dip and left-lateral slip. (d) Planar and vertical fault with right-lateral slip. Root mean square values are in centimeters.

View larger version (115K): [in a new window]   Figure 6. (a)–(b) Descending and ascending interferograms predicted by the best model (model 4B). (c)–(d) Two of the residual interferograms obtained after subtracting the synthetic interferograms from the observed data. (e) Line-of-sight profiles comparing the model with the data. Arrows show the position of the modeled fault.

View larger version (77K): [in a new window]   Figure 7. Strike-slip distribution on the modeled fault (model 4B). White arrows show the direction of motion of the eastern block relative to the western one (view toward southwest).