Foreword On the basis of the detailed macroseismic study of the 21 May, 2003 Zemmouri earthquake (Mw= 6. 8), we measured the epicentral distance to about 600 intensity-observation localities and analysed the resulting dataset by regression procedures. The earthquake that is the most destructive event in Algeria since 1980 caused 2,280 casualties and the collapse and serious damage of more than 30,000 buildings. The coastal epicentre location makes the earthquake an important case study useful for a better understanding of the seismic hazard of the Algiers region. Different regression curves are calculated using various directions and the resulting attenuation distribution shows diverse behaviours related to the specific geological structures. Significant variations of intensity are related to the sedimentary versus basement and rocky areas. These results extend our knowledge on the interaction between the damage distribution and the local soil conditions. Moreover, the comparison of the Zemmouri earthquake with historical offshore and coastal seismic events, the 1856 Djidjelli earthquake to the east and the 1891 Villebourg earthquake to the west, allows us to infer new conclusions on the seismogenic sources along the Algerian coastal area.