AN INTEGRATED GEOPHYSICAL INVESTIGATION OF RECENT SEISMICITY IN THE AL-HOCEIMA REGION OF NORTH MOROCCO

Data produced by the Moroccan national seismological network and marin e seismic reflection profiles an used to investigate the most seismica lly active region in Morocco, located on the Mediterranean coast at th e intersection of the Rif mountain belt and the submarine Alboran Ridg e. This region, in the vicinity of the city of Al-Hoceima, marks an ea st-west transition in the marine and land deformation styles of the di stributed plate boundary between Africa and Iberia, and was the site o f an M-w = 6.0 earthquake on 26 May 1994. The epicenter of the Al-Hoce ima earthquake is relocated onshore, refining the initial submarine lo cation close to the Alboran Ridge. The spatial distribution of foresho cks and aftershocks shows a NE-SW trend that continues partly offshore and is subparallel to the earlier, yet still prominent, Miocene geolo gic structural trend. The predominantly strike-slip focal mechanism fo r the Al-Hoceima event is characteristic of earthquakes in the region. Marine seismic reflection profiles that intersect the offshore region of seismicity image active high-angle faults with possible strike-sli p components. The seismicity trend is not directly related to the subm arine Alboran Ridge or the geomorphologically prominent Nekor fault. D eformation appears to be occurring on a number of subsidiary strike-sl ip faults that together compose a NE-SW zone of distributed shear. The distributed strike-slip and documented normal faulting taking place i n the eastern Rif mountains, although characteristic of the Rif region , are in contrast to the thrusting style of deformation that occurs fa rther to the east in the Algerian Tell Atlas. This may be related to t he reported lateral variations and evolution of the convergent plate b oundary in these regions during the Neogene and Quaternary times.