RECENT SEISMIC ACTIVITY IN THE NORTHERN RED-SEA

Recent seismicity and swarm activity in the northern Red Sea have been examined in relation to the tectonics and structures indicated by surface geology and marine magnetic anomalies. Seismicity appears to be low compared to the rest of the Red Sea. Sixty eight earthquakes recorded during the period 1964-1993 had body-wave magnitudes between 3.8 and 6. On 18 February 1992, a swarm of earthquakes began in the northern Red Sea and lasted for about 5 days. More than 180 local earthquakes were detected between 25.79 degrees-26.89 degrees N latitudes and 34.74 degrees-35.57 degrees E longitudes, 12 of which were discernible enough on seismograms to establish epicenters and magnitudes. The majority of seismic activity of this swarm is clustered in the area located between lat. 26.7 degrees and 27.3 degrees. The most remarkable aspect of this earthquake swarm sequence is the migration of epicenters northward by about 100 km in 5 days with focal depths less than 20 km. This study and historical data confirm that the relatively low level of seismicity should not be used as an argument for minimizing the probability of seismic hazard. This swarm may release energy that can be accumulated to cause larger events in the future. This study, however, does not agree with the previous idea which states that the northern Red Sea is considered to be a seismic gap, where the faults are locked and do not generate earthquakes.