Crustal deformation of the southeastern corner of Egypt derived from geodetic data (original) (raw)
Related papers
Recent crustal deformation and seismicity studies at Abu-Dabbab area, Red Sea, Egypt
Arabian Journal of Geosciences, 2013
The Abu-Dabbab area is characterized by high seismicity and complex tectonic setting; for these facts, a local geodetic network consisting of 11 geodetic benchmarks has been established. The crustal deformation data in this area are collected using the GPS techniques. Five campaigns of GPS measurements have been collected, processed, and adjusted to get the more accurate positions of the GPS stations. The horizontal velocity vectors, the dilatational, the maximum shear strains, and the principal strain rates were estimated. The horizontal velocity varies in average between 3 and 6 mm per year across the network. The results of the deformation analysis indicate a significant contraction and extension across the southern central part of the study area which is characterized by high seismic activity represented by the clustering shape of the microearthquakes that trending ENE. The north and northeastern parts are characterized by small strain rates. This study is an attempt to provide valuable information about the present state of the crustal deformation and its relationship to seismic activity and tectonic setting at the Abu-Dabbab area. The present study is the first work demonstrating crustal deformation monitoring at the Abu-Dabbab area. The time interval is relatively short. Actually, these results are preliminary results. So, the continuity of GPS measurements is needed for providing more information about the recent crustal deformation in that area.
NRIAG Journal of Astronomy and Geophysics, 2013
A local geodetic network consisting of eleven benchmarks has been established to study the recent crustal deformation in the Abu-Dabbab area. Seven campaigns of GPS measurements have been collected started from October 2008 and ended in March 2012. The collected data were processed using Bernese version 5.0, and the result values were adjusted to get the more accurate positions of the GPS stations. The magnitudes of horizontal displacements are variable from one epoch to another and in the range of 1-3 (±0.2) mm/yr. Due to the differences in rates of the horizontal displacement; the area is divided into two main blocks. The first one, moves to the east direction of about 3 mm/yr, while the second block, moves to the SW direction of about 6 mm/yr. According to the strain fields that were calculated for the different epochs of measurement, the main force is compression force and is taken the NW-SE to NWW-SEE direction. This force could be because of local and regional tectonic processes affecting on the study area. The maximum values of compression stress are found in the southern central and western part of study area. Estimated accumulation of this strain energy may be considered as an indicator of the possibility of earthquake occurrence. From the seismic tomography study, the 3D Vp and Vp/Vs crustal models indicate high Vp/Vs values forms an elongated anomaly, in the central part of the study area, that extends from a depth of 12 km to about 1-2 km of depth is obtained. By using this crustal model in relocations all seismicity informed that most of the seismicity strongly tend to occur in a cluster manner exactly
Deformation analysis of Great Cairo deduced from potential and GPS data, Egypt.
NRIAG Journal of Geophysics, 651-680., 2009
Detecting crustal movements using the Global positioning system (GPS) has been applied at different seismically active areas in all the world. Egypt is recognized as a moderate earthquake activity region with frequent moderate events. Most of its seismicity is concentrated at its northern part and around greater Cairo. For instance, there have been earthquake activities in the southwest of Cairo region (Dahshour area) since 1847. In order to monitor crustal deformation around this active area, a local geodetic network consists of 8 geodetic points were established in the year 2004, around the active faults. Three campaigns were performed and processed using Bernese GPS software version 5.0. The aim of the present study is to determine the tectonic elements presented and to throw lights upon the geodynamic regime of the study area. The velocity vectors for each epoch of observations were calculated and deformation analysis was performed. The horizontal velocity varies in average between 1 and 8 mm per year across the network.
Present stage of recent crustal movements and seismicity within Greater Cairo area, Egypt
2014
Greater Cairo and the Nile Delta are considered very important, high-density population areas. The subject of the research work is dealing with recent crustal movements and its relation to seismicity and tectonics setting. A Global Positioning System (GPS) network consisting of 11 benchmarks covering Greater Cairo and the southern part of the Nile Delta was established in 1996. Different campaigns surveyed the network. In this study, we used ten measurements collected during the period from 2004 to 2010. The data were processed using Bernese 5.0 software to derive velocity vectors and principal components of crustal strains. The horizontal velocity varies in average between 3 and 6 mm per year across the network. Rate of the accumulated strains in the southern part of Greater Cairo varies from low to moderate. The low strain rates and low level of earthquakes occurrence in the present interval in the Nile Delta area indicated that the rate of the deformation in this area is small. The result from coupling GPS and seismic data indicates that the southern part of the area is seismo-active area when compared with the other parts in the network areas. The paper gives information about the present state of the recent crustal movements within Greater Cairo area to understand the geodynamics of that area. This study is an attempt to build a basis for further development of seismic catastrophic risk management models to reduce a risk of large catastrophic losses within the important area.
The Nile Valley in Egypt is located to the west of the Red Sea Rift and to the south of the Mediterranean Sea. Recently, some moderate earthquakes were occurred along the Nile Valley at the eastern and western side. 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. A program of studying the recent crustal movements in Egypt has been started since 1984 to cover some areas which are characterized by the occurrence of felt Earthquakes. One of these areas is the Nile Valley. About 6 moderate earthquakes with magnitudes more than 4 were occurred on both sides of River Nile. The present study aimed to determine the recent crustal movement parameters along the Nile Valley using the Global Positioning System (GPS) measurements. To achieve this mission, a GPS network consisting of ten geodetic stations has been established on both sides along the Nile Valley area. GPS measurements have been collected from 2007 to 2012. The collected data were processed using Bernese 5.0 Software. The result of the data analysis indicates that the rate of local velocity is small ranging from 1 to 4 mm/year. This rate is consistent with the low rate of occurrence of recent earthquakes activity along the Nile Valley area. But, the results obtained from the calculation of the regional velocity indicated that the velocity of the GPS stations including the African Plate motion is about 25 mm/year in the northeast direction which is consistent with the African Plate motion direction.
NRIAG Journal of Astronomy and Geophysics, 2016
The northern part of Egypt is a rapidly growing development accompanied by the increased levels of standard living particularly in its urban areas. From tectonic and seismic point of views, the northern part of Egypt is one of the interested regions. It shows an active geologic structure attributed to the tectonic movements of the African and Eurasian plates from one side and the Arabian plate from the other side. From historical point of view and recent instrumental records, the northern part of Egypt is one of the seismo-active regions in Egypt. The investigations of the seismic events and their interpretations had led to evaluate the seismic hazard for disaster mitigation, for the safety of the densely populated regions and the vital projects. In addition to the monitoring of the seismic events, the most powerful technique of Global Navigation Satellite System (GNSS) will be used in determining crustal deformation where a geodetic network covers the northern part of Egypt. Joining the GPS Permanent stations of the northern part of Egypt with the Southern part of Europe will give a clear picture about the recent crustal deformation and the African plate velocity. The results from the data sets are compared and combined in order to determine the main characteristics of the deformation and hazard estimation for specified regions. Final compiled output from the seismological and geodetic analysis will throw lights upon the geodynamical regime of these seismo-active regions. This work will throw lights upon the geodynamical regime and to delineate the crustal stress and strain fields in the study region. This also enables to evaluate the active tectonics
EVALUATION OF THE CRUSTAL DEFORMATION IN THE GULF OF SUEZ REGION USING GPS TECHNIQUES
Recently, one of the important methods for studying crustal deformation, by means of space techniques, is the Global Positioning System (GPS). The earth's crust deformation attains values of only few mm/yr and can be determined according to the spatial and time density of the measurements as well as their degree of accuracy. A geodetic network consists of 11points was established early in 1997 in southern Sinai . This network was observed six times in different campaigns during the period 1997 – 2003. The observed data were analyzed using Bernes 4.2 software to determine velocity vectors along the Gulf of Suez and Sinai Peninsula. The estimated horizontal velocity vectors in the International Terrestrial Reference Frame (ITRF2000) show that the velocity of Sinai Peninsula ranges from 1.8 to 2.3± 0.5 mm/yr in the NE direction. This velocity is consistent with those predicted by the model NUVEL- 1A in the same direction but smaller in magnitude. The strain Tensor program was used to estimate the principal axes of strains. The principal axes of the strain indicate that the studied region is mainly divided into two areas: western part, around Gulf of Suez, where extensional strain is predominant and the eastern part, around the Gulf of Aqaba, where compressional strains prevail. Principal axes of the strain indicate that an extensional force is acting along the Gulf of Suez in NE-SW direction. Moreover, the principal axes of strains show a good correlation with the directions obtained from earthquake focal mechanisms.
Journal of Geodynamics, 2010
The proper evaluation of crustal deformations in the Aswan (Egypt) region is crucial due to the existence of one major artificial structure: the Aswan High Dam. This construction induced the creation of one of the major artificial lakes: Lake Nasser, which has a surface area of about 5200 km 2 with a maximum capacity of 165 km 3 . The lake is nearly 550 km long (more than 350 km within Egypt and the remainder in Sudan) and 35 km across at its widest point. Great attention has focused on this area after the November 14, 1981 earthquake (M L = 5.7), with its epicenter southwest of the High Dam.
GPS-derived velocity and crustal strain field in the Suez-Sinai Area, Egypt
Bull. Earthq. Res. Inst. Univ. Tokyo, 2005
Five GPS measurements collected in campaign mode during the period +331῍,**, are analyzed to derive velocity vectors and principal components of crustal strains along the Gulf of Suez and in the southern part of the Sinai Peninsula, Egypt. Estimated horizontal velocity vectors in ITRF,*** are found to be in the range of ,3῍-/ mm/yr with an uncertainty level in the order of +῍, mm/yr (3/ῌ confidence level). Then, estimated velocities are converted into a kinematic reference frame (Prawirodirdjo and Bock, ,**.) to discuss crustal deformation relative to the Eurasian plate. Least-Squares prediction (LSP) technique is employed to segregate signal and noise from velocity vectors. Estimated signals are used to reconstruct strains, dilatations, maximum shear strains, and principal axes of strains. Strains obtained might portray active tectonic environments in the region under study. (+) Dilatational strains indicate that the region under study is mainly divided into two areas : the western part around the Gulf of Suez where extensional strain is predominant, and the eastern part around the Gulf of Aqaba where compressional strains prevail. (,) Maximum shear strain is mostly accommodated at the Gulf of Suez and Gulf of Aqaba. Distribution of seismicity shows high consistency with high shear strain areas. The estimated dilatation strain rate and the maximum shear strain rate are both *.,/ Micro-strain/yr on average. (-) Principal axes of the strains indicate that an extensional force is acting along the Gulf of Suez in the NE-SW direction. Moreover, the principal axes of strains show a good correlation with the SHmax directions obtained from earthquake focal mechanisms and borehole breakouts.