Crustal Strains Field in the Vicinity of the northern part of nasser lake, egypt,as deduced from GPS measurements and its tectonic implications

The studied area in this research is occupied by the Nasser Lake, whichhas started to fill due to the Aswan High Dam construction early in 1964, andto form one of the largest man-made reservoirs in the world. The Aswan HighDam is considered as a unique structure among all large irrigation and electricpower projects in the world. It is a rockfill and concrete type structure, J J 0 mhigh and located above the first cataract of the Nile, 15 km south of AswanCity. The water level in the reservoir has risen gradually with annual irrigationcycles and reached a maximum level of 177.48 m in November 1978 with acapacity of 133.8 krn’. An earthquake of magnitude 5.3 (Ms) took place on 14November, J 981 along the most active part of the E- W Kalabha fault bay, thelargest bay of the lake. The filling of such large reservoir changes the stresssystems either through increasing vertical compressional stress by loading orincreasing pore pressure through the decrease of the effective normal stress.The GPS technique has become the geodetic method of choice forstudying a wide range of geophysical phenomena. GPS measurements are nowin use to determine the motion of the Earth’s tectonic plates, and to studydeformation around active faults. Around the northern part of the Nasser Lake,the GPS measurements were initiated in 1997. A GPS network consisting ofII sites has been established by the Notional Research Institute of Astronomyand Geophysics (NRIAG) to investigate the crustal deformation in thisimportant area. The campaign observations have been repeated in the area twotimes a year between 1999 and 2008.In the present study, GPS measurements collected in campaign modeduring 1999 - 2008 have been analyzed using Bernese software (Version 5.0)to derive velocity vectors around northern part of the Nasser Lake, Egypt.Velocity vectors obtained in ITRF2005 indicate that the magnitude of thehorizontal velocity is in the range of 28.0 - 30.5 mm/yr with an average of.