Assiut university researches
Recent Crustal Movement Studies Along the
Nile Valley, Egypt
‫درا سات ال تحرك ات ال حدي ثة ل ل ق شرة األر ض ية ع لى‬
.‫طول وادى ال ن يل م صر‬
Mohamed Abd El Fadeel Manssour Rashwan
‫محمد ع بدال ف ض يل م ن صور ر شوان‬
Mostafa Mahmoud Youssef, Awad Abdel-Khalek Omran, Salah
Mohamed Mahmoud, Hassan Ahmed Khalil, Matthias Bwcker
‫ ح سن أحمد‬،‫ ص الح محمد محمود‬،‫ عوض ع بدال خال ق عمران‬،‫م صط فى محمود ي و سف‬
‫خ ل يل‬
Abstract:
Nowadays, Great efforts are devoted to the development of
the Nile Valley because this area is highly populated and
includes many tourism places, which are very important for
our national income. Also, it contains different factories and
strategic projects such as dams, electric power stations and
settlement of new cities in different localities on both sides of
the Nile Valley. So, the study of recent Crustal movements
and seismic activities are important along this vital area of
Egypt. The Nile Valley in Egypt is located west of the Red
Sea rift and south of the Mediterranean Sea seismic zone.
Red Sea rift is characterized by a small to moderate size
earthquake activity. Large earthquakes from the
Mediterranean Sea seismic zone, as well as those originating
in Egypt cause dramatic damage in the Nile Valley area.
Tectonically, the Nile Valley is controlled by NW-SE, NE-SW,
E-W and N-S tectonic trends due to the exerted forces and
stresses. Records of historical earthquakes affecting that
area are extended over the past 4800 years. Study of recent
crustal movements along Nile Valley aims to determine the
displacements, and their directions and the strain rates using
GPS techniques. To achieve this mission successfully, a local
geodetic network consisting of 12 geodetic stations has been
established. Four campaigns of GPS measurements have
been carried out XXI starting from May 2007 to November
2009 (each campaign was measured in four days long
continuous observation). Collected data were processed
using Bernese version 5.0 considering all constraint
conditions needed for analysis. In a least squares adjustment
precise coordinates and velocities for the network sites were
estimated. Monika deformation program is used for the
computation of the deformation field in the study area. The
horizontal displacement vectors, the dilatational, the
maximum shear strains and the principal strain rates were
estimated. The magnitudes of horizontal displacements for all
epoch’s ranges from 1-5 mm/yr. Some stations of the network
indicate a significant value while other stations illustrate
negligible values for the movement through all periods of
observations. The magnitudes of the movements are
distributed inhomogeneously over the area. The seismicity
map of the study area confirmed that the Nile Valley lies
along a seismoactive belts (Gorshkov, 1963). Most of the
seismic activity concentrated in significant areas. Focal
mechanisms solution (FMS) was carried out for number of
events using the polarity of P- waves. The majority of the
earthquakes focal mechanisms were normal with a strike-slip
component or strike-slip faulting events and another one with
small minority exhibits a reverse fault. According to the stress
and strain fields which were calculated for the different
epochs of measurement it is worthy to be mentioned that the
Nile Valley area suffers from stress XXII and strain. The
direction of extension strain is prevailing in the north of study
area are NNW-SSE to NW-SE. Compressional strain is
dominated in south area with directions NNW-SSE and ESEWNW. The causing force may be due to local and regional
tectonic processes affecting the study area. The maximum
values of compressional stress are found in the southern
central and western part of the study area. The resulting
average of strain extension for all epochs is about 0.10 μs/yr.
Compressional strains of all epochs, reaches about 0.051
μs/yr as NNW–SSE to ESE-WNW direction. Estimated
accumulation of this strain energy could be considered as an
indicator of the possibility of earthquake occurrence. The total
amount of the maximum shear strain accumulation during the
observation interval was relatively small. The results
demonstrate that the maximum shear strains increases
towards the north direction and decreases towards the south
and southeast directions. The dilatational strains in the
southern part and the middle east of the region are
dominated by shortening while the extensive strain rates are
prevailed in the northwestern part and in the area close to the
Nile Banks. Generally, the low strain rates and low level of
earthquake occurrence in the present interval in the southern
part indicate that the rate of the deformation in this area is
rather small. XXIII The results of these movements represent
the form of the preliminary dynamic model for the deformation
which occurred at Nile Valley area during the different epochs
of measurements. These results may agree with the results
from the seismic events analysis for the Nile Valley area. This
thesis is considered as a preliminary and first study that
presents the surface crustal deformation integrated by
seismicity and focal mechanism of earthquakes along the Nile
Valley area.