GROUND PENETRATING RADAR ANALYSIS OF SEISMIC HAZARD IN AQABA, JORDAN

The city of Aqaba is situated along part of the Dead Sea Transform (DST) where a major NE-trending, strike-slip fault (the Aqaba fault) that originates in the Gulf of Aqaba terminates under the city. Previous trenching investigations show that strain is transferred from the Aqaba fault onto four normal- to olique-slip cross faults that produce active tectonic subsidence at the head of the Gulf. Ground penetrating radar (GPR) surveys were conducted at two trenched cross-fault exposures. GPR measurements made with 100 MHz and 50 MHz antennas identified two strong, planar, steeply dipping, reflectors coincident with the fault location identified from the trench exposure. The shape of the GPR record indicates the direction of dip on the fault. Offsets in planar radar reflectors were also apparent in the radar records. A GPR profile within the city of Aqaba was conducted along a 300 m line postulated to intersect the main strike-slip fault, based on limited historical and geological data. A distinct radar signature, very similar to that observed over the trenched fault exposure, was recorded. Nine additional GPR profiles were conducted in an attempt to delineate the extension of the Aqaba fault on a 2.7 km traverse through the city. Seven of these profiles contained a GPR signature similar to that recorded over the known fault exposures. When plotted on a map, these GPR signatures define a near-straight line, assumed to define the location of the Aqaba fault under the city. The geophysical delineation of this major active fault has profound implications for seismic hazard analysis within Aqaba.