CONSTRAINING THE CRUSTAL DEFORMATION AROUND THE NORTHERN PART OF LAKE NASSER USING GPS TECHNIQUES AND SEISMOLOGICAL DATA

Mahmoud, S.M.; Radwan, A.M.; Tealeb, A.A.; Omran, A.A.; Bary, R.A. Fathel-; Rayan, A.

doi:10.21608/jegs.2006.378467

CONSTRAINING THE CRUSTAL DEFORMATION AROUND THE NORTHERN PART OF LAKE NASSER USING GPS TECHNIQUES AND SEISMOLOGICAL DATA

Document Type : Original Article

Authors

¹ National Research Institute of Astronomy and Geophysics, Helwan

² Geology Department, Faculty of Science, Assiut University.

³ National Research Institute of Astronomy and Geophysics, Helwan.

10.21608/jegs.2006.378467

Abstract

On November 14, 1981 an earthquake with magnitude Ms= 5.3 occurred along Kalabsha fault, 60 km southwest of Aswan City, Egypt. As the High Dam is the single dam which controls the whole country, a program for monitoring recent crustal movements in Kalabsha area has been started in cooperation between the National Research Institute of Astronomy and Geophysics (NRIAG) and the High Dam Authority.
Analysis of the composite focal mechanism solution of the studied five different seismic zones in Aswan region showed that the focal mechanism is almost strike-slip faulting.
To monitor the crustal deformation around this area and to find its association with the seismic activity , a geodetic network consisting of 11 points was established early in 1997 on both sides of the northern part of Lake Nasser. This network was observed eight times in different campaigns during the period 1997 – 2004. The observed data was analyzed using Bernese 4.2 software to derive velocity vectors along both sides of Lake Nasser and to calculate the principal axes of strains.
The mean velocity for each year was nearly 2 mm/yr in direction nearly NE which is almost consistent with the direction of the African plate. These values of deformations are relatively small. Therefore, the area does not suffer from remarkable deformation except some areas around Kalabsha and Seiyal faults.
From the strain results, the northern part of Lake Nasser may be divided into three main parts: The northern part suffers from high compressional strains in northeast-southwest direction of about 0.1 μs/yr; the southern part of Lake Nasser has high extensional strains in the same direction of about 0.1 μs/yr; and the middle part of the study area including Kalabsha area has both low compressional and extensional strains in east – west direction and this may due to the energy released through the faults in this area.