than 500 local earthquakes (ML Q 4.85) occurred in the Gulf of Aqaba area between latitudes 29'00 ' and 29'25' and longitudes 34'30' and 34'45'. Most of the activity including the largest shocks was restricted t o the area between latitudes 29'07 ' and 29'15' and longitudes 34'33' and 34'42' where the NW Atiya regional dyke crosses the area and is horizontally displaced by NE strike-slip faults. The first-motion directions of four large shocks, including the largest, at both UNJ and HLW stations are in agreement with a strike-slip mechanism at a NE-trending fault in this area. The b value showed a temporal increase with time from 0.43 to 0.69. This, together with other geological and geophysical observations may indicate that subsurface magmatic activity has affected the stressed crustal rocks, thus triggering earthquake activity.This swarm and historical information indicate that the Gulf of Aqaba-Dead Sea Jordan transform is characterized by both swarm and foreshockaftershock types of seismic activity and therefore the relatively large proportion of non-seismic slip along the southern part of this transform may actually be higher if swarm-type activities are considered. IntroductionAn earthquake swarm occured in the Gulf of Aqaba area (Fig. l), in the period 1983 January 21 to April 20, during which 60 shocks (1.7 Q M L Q 4.85) were recorded on the Jordan University Seismological Station, some 350 km distant. With no distinctive main shock, the level of activity fluctuated with time, reaching its highest on February 3 when a few large shocks (including the largest of the swarm) occurred and were widely felt in the Saudi town of Haql, Aqaba and the surrounding region, thus causing panic and concern. On February 8, a temporary seismic station was installed near Haql. Within its 72 days of operation, more than 500 shocks (0.0 G M L G 3.5) were recorded, showing a decreasing level of activity with time. By April 20, the level of seismicity in the Gulf seemed to have returned to normal.

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Extensive geophysical investigations have been carried out at the Mahd adh Dhahab gold mine, Kingdom of Saudi Arabia, by the U.S. Geological Survey Saudi Arabian Mission as part of a multidisciplinary study of the district.The three major objectives of the study were: 1) to define unexposed areas of probable sulfide mineralization for further exploration; 2) to infer the geologic relations beneath the covered areas surrounding Jabal Mahd adh Dhahab; and 3) to provide further constraints on structural and genetic models of the geologic history.The study area measures 1.5 km in a north-south direction by 2.9 km in an east-west direction and is centered approximately on the mine workings. Work was completed during the period between mid-1973

The Wadi Mandahah mine is an ancient gold mine that probably was worked during the Abbas id Caliphate in the eighth and ninth centuries A.D.The mine is in complexly folded and faulted metavolcanic and pyroclastic rocks of the Baish group of Precambrian age. The mineralized outcrop consists of weakly limonitic gossan containing malachite and chrysocolla veinlets.The deposit has been mined in shallow pits and trenches. Geochemical and geophysical surveys indicated weak mineralization along shear zones and in the nose of a fold that plunges southwest. Four holes aggregating 887.4 m were drilled to explore the mineralized zones below ancient workings. No significant ore bodies were discovered.

During the course of a seismic refraction investigation in Saudi Arabia, an unexpected high level of microearthquake activity was detected near the border of the Red Sea and near the transition from oceanic to continental crust. The data is not adequate to determine fault plane solutions nor to relate the earthquakes to specific structures, but the existence of microearthquakes at this location suggest that there is a significant level of tectonic activity at a point 200 km from an axial trough of the Red Sea. These data, combined with other recent geological observations, may be an important clue to the understanding of continental rifting. The data suggest the need for a more thorough investigation of the earthquake hazard along the shores of the Red Sea.