- Copyright © 1999, by the Seismological Society of America
Source mechanisms of the Melilla, Alhoceima, and Mascara earthquakes, including fault-plane solutions, waveform modeling, and spectral analysis, are presented. Strike-slip solutions have been obtained for the Melilla and Alhoceima earthquakes and reverse faulting for Mascara. Teleseismic P-wave inversion, using broadband data, show a complex mechanism for the Alhoceima earthquake formed by two subevents at very shallow depth (7 and 8 km) and scalar seismic moments of 1.1 × 10e + 17 N-m and 4.8 × 10e + 17 N-m. The Mascara earthquake was a single event, with a shallow depth (4.5 km) and a scalar seismic moment of 3.3 × 10e + 17 N-m. Results of the Alhoceima, Melilla, and Mascara earthquakes, together with 53 focal mechanisms in the region, show a regional stress regime that corresponds to horizontal compression in a NW-SE direction, associated with the convergence between Eurasia and Africa. A change of the stress regime in the plate boundary of the Ibero-Maghrebian region has been found.