f BASIN DEFINITION USING GRAVITY AND MAGNETIC DATA: CASE STUDY FROM EL QAA PLAIN, SINAI, EGYPT

The arid and semiarid areas in the Middle East have always faced issues of scarcity of fresh water resources coupled with the absence of a comprehensive understanding of the geologic, structural, and hydrogeologic controls on the development and preservation of these resources. Egypt is a country that seeks additional fresh water resources to support its increasing population and to continue modernization and development. This study, addressed the geologic and hydrologic setting of one of the Quaternary fresh groundwater aquifers, the El Qaa Plain aquifer, located in SW Sinai. This is a half-graben related to the tensional opening of the Gulf of Suez. A total of 381 ground gravity stations resulted from three phases (2003, 2005, and 2011) of data collection over an 85km x 20km area in the El Qaa Plain. The station interval ranged from 0.5 to 1.0 km while the profile separation ranged from 1.0 to 5.0 km. The gravity minimum of -20.0 mGal is similar to that of valleys in the Basin and Range province. Additionally, 763.0 km of airborne magnetic data were acquired in 1998, covering a 65km x 15km area with 26 survey lines having line separations of 1.0 km. Both gravity and magnetic data were processed in the Oasis Montaj environment. The Complete Bouguer Anomaly and leveled total magnetic field maps show two connected sub-basins. The 2-D modeling of both gravity and magnetic data indicates basin fill in the graben area with maximum thickness of 3.0 km along the graben axis. The Analytic Signal and the Euler deconvolution (standard and located) supported these results. The volume of water in storage is being estimated by integration of the anomalous residual gravity after regional tilt has been removed.