Contributors: University of Ibn Tofail: E. A. Toto, M. El Basri, M. Hafid, M. Benammi CNRST: A. Birouk, A. El Mouraouah, A. Ibenbrahim, M. Kasmi

MOTIVATION FOR UNDERTAKING GEOPHYSICAL SURVEY Analysis and interpretation of surface geology and geomorphology data were suggestive of the presence of important fault structures Because reactivation of these neotectonic faults is likely to induce destructive earthquakes, geophysical tools were the most appropriate : 1.Fist to affirm or to infirm the presence of these actively seismic features 2.To unravel the geometry and attitude of these hazard-inducive structures at depth Analysis and interpretation of surface geology and geomorphology data were suggestive of the presence of important fault structures Because reactivation of these neotectonic faults is likely to induce destructive earthquakes, geophysical tools were the most appropriate : 1.Fist to affirm or to infirm the presence of these actively seismic features 2.To unravel the geometry and attitude of these hazard-inducive structures at depth

Emplacement of the profiles of seismic refraction and electric resistivity tomography Location of the study area

S N Fault displacing recent rock units as evidenced by the outcrops

Seismic refraction tomography data acquisition in the field

Tomography seismic refraction equipment as displayed in the field

Field acquisition of electric resistivity tomograhy data Field acquisition of electric resistvity tomography data

Electric resistivity tomography data inversion process

-The seismic and electric resistivity tomography data conspicuously image thrust faults delimiting wedges or thrust sheet-like geometries -- The inverted seismic data display high velocity wedges overriding low velocity material -- In the inverted resistivity sections, relatively high resistive wedges are contiguous with less resistive material with thrust faults in between -- outcropping thrust faults are ramping up rock unit sections up to the surface into antiforms and synforms folds where recent growth strata, deposited contemporaneously with the deformation, can provide a clue to the deformation dating and average slip determination. -The seismic and electric resistivity tomography data conspicuously image thrust faults delimiting wedges or thrust sheet-like geometries -- The inverted seismic data display high velocity wedges overriding low velocity material -- In the inverted resistivity sections, relatively high resistive wedges are contiguous with less resistive material with thrust faults in between -- outcropping thrust faults are ramping up rock unit sections up to the surface into antiforms and synforms folds where recent growth strata, deposited contemporaneously with the deformation, can provide a clue to the deformation dating and average slip determination.

In conclusion: The applied geophysical tomography methods efficiently captured the main structures of the investigated site The internal structure under the site is that of thrust sheets that characterize fault –and-fold thrust belts in the building of mountains chains The faults are displacing also the superficial unit rocks, which point to very likely recent activities along these structures Since one can not ascertain that these faults represent the actual deformational front of the Rif mountains southwards, more detailed geological and geophysical investigations are in order to dig up more quantified information on this structures that would be beneficial in the tsunami and seismic hazard assessment and in the delineation of the real position of the deformation front. In conclusion: The applied geophysical tomography methods efficiently captured the main structures of the investigated site The internal structure under the site is that of thrust sheets that characterize fault –and-fold thrust belts in the building of mountains chains The faults are displacing also the superficial unit rocks, which point to very likely recent activities along these structures Since one can not ascertain that these faults represent the actual deformational front of the Rif mountains southwards, more detailed geological and geophysical investigations are in order to dig up more quantified information on this structures that would be beneficial in the tsunami and seismic hazard assessment and in the delineation of the real position of the deformation front.