Journal of Seismology 6: 257–277, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands. 257 Evaluation of the seismic hazard of Lebanon M. Harajli, S. Sadek & R. Asbahan Department of Civil and Environmental Engineering, American University of Beirut Received 12 January 2001; accepted in revised form 11 September 2001 Key words: earthquake engineering; ground acceleration; hazard analysis; seismic hazard; seismic zoning Abstract This paper presents the results of a study undertaken to determine the seismic hazard of Lebanon. The seismic hazard evaluation was conducted using probabilistic methods of hazard analysis. Potential sources of seismic activities that affect Lebanon were identified and the earthquake recurrence relationships of these sources were developed from instrumental seismology data, historical records, and earlier studies undertaken to evaluate the seismic hazard of neighboring countries. The sensitivity of the results to different assumptions regarding the seismic sources in the Lebanese segment and choice of the attenuation relationship was evaluated. Maps of peak ground acceleration contours, based on 10 percent of probability of exceedance in 50 years and 100 years time spans, were developed. Introduction A quick review of the seismic activity in Lebanon and the Eastern Mediterranean clearly demonstrates that this part of the world has been shaken since 2000 B.C. by strong earthquakes that destroyed thousands of structures and caused severe casualties and loss of human life in present day Lebanon, Syria, Jordan, Israel and Palestine. Three earthquakes stand out in the history of seismic activities in Lebanon: the earth- quakes of 551 A.D., 1202 A.D and 1759 A.D (two events). The magnitudes of these earthquakes were es- timated, based on historical accounts, to be in excess of 7.0, and caused destruction in most coastal cities including Beirut, Tripoli, Jubail, Saida, and Tyre as well as the ancient city of Baalbeck. Occupying 225 km of the 600 km long segment making up the Eastern Mediterranean coastal region, Lebanon lies right across an estimated 1000 km long fault which extends from the seafloor spreading in Red Sea to the Taurus mountains in southern Turkey (Fig- ure 1). This fracture system, known as the levantine or Dead Sea system (Beydoun, 1977), is an extremely important tectonic feature, which accounts for the bulk of seismic activity in the Eastern Mediterranean. Figure 1. The levantine fracture system.