Abu Dabbab Area Research Articles

Origin and Heavy Metals of Plagio-Granites in Egyptian Shield Oceanic Complexes: A Case Study of Abu Dabbab Area, Central Eastern Desert, Egypt

Several outcrops of felsic melt, commonly known as oceanic plagio-granites, appear as melt pockets, irregular bosses, and dikes. Three main rock successions were exposed in the Abu Dabbab area: ophiolitic sequence, island arc assemblage, and rare metal-bearing albite granites. Plagio-granite is composed mainly of plagioclase and quartz, and chemically contains high SiO2, Al2O3, and Na2O values. The petrogenetic and geochemical studies concluded that the magmas of plagio-granites and associated felsic rocks were derived from partial melting of highly depleted mantle harzburgite and/or pre-existing oceanic crustal rocks (basalts and/or gabbros). The geochemical characteristics reveal that Abu Dabbab plagio-granites are identical to the typically low-K series of ophiolitic complexes and resemble the ocean ridge granites. Elements such as Co, Nb, Pb, and Nd in Abu Dabbab plagio-granites have high Clarke concentrations (more than 1.88). This indicates Abu Dabbab plagio-granite derived from partial melting of pre-existing oceanic crustal rocks. The average concentration values of 238 U and 232 Th are lower than those of the world’s average and the average activities in granitic rocks. The scope of estimated exercises generally contrasted as their quality in rock tests relies upon their physical, synthetic, and geo-concoction properties and the appropriate condition.

Morpho-tectonic Assessment of the Abu-Dabbab Area, Eastern Desert, Egypt: Insights from Remote Sensing and Geospatial Analysis

The Abu-Dabbab area, located in the central part of the Egyptian Eastern Desert, is an active seismic region where micro-earthquakes (≈ML < 2.0) are recorded regularly. Earthquake epicenters are concentrated along an ENE–WSW trending pattern. In this study, we used morphological indexes, including the valley floor width-to-valley floor height ratio (Vf), mountain front sinuosity (Smf), the asymmetry factor index (Af), the drainage basin shape index (Bs), the stream length–gradient index (SL), hypsometric integral (Hi) water drainage systems, and a digital elevation model analysis, to identify the role of tectonics. These indexes were used to define the relative tectonic activity index (RTAI), which can be utilized to distinguish low (RTAI < 1.26), moderate (RTAI = 1.26–1.73), and high (RTAI > 1.73) tectonic activity signals all over the study area. Firstly, our results indicate low to medium tectonic activity and general anomaly patterns detected along the major tectonic zones of the study area. Secondly, based on most of the low to medium tectonic activity distributed in the study area and the detected anomalies, we discuss two potential drivers of the seismicity in the Abu-Dabbab area, which are fault-controlled and deep-rooted activities.

Analysis and interpretation of geophysical data to delineate the geologic structures of Abu Dabbab area, South Eastern Desert, Egypt

ABSTRACT The present study aims to identify the geologic structure of the Abu Dabbab area. The previous work state that the study area contains different ore minerals such as Tantalum, Niobium, Cassiterite, Gold, and sulphides. Processing, analysis, and interpretation of aeromagnetic and recorded seismic events data of the study area were to define the seismic activity zones and the main trend in the study area and its relation with ore deposits distribution. The area is controlled by different structural elements of trends NE-SW, NNW-SSE, and E-W. The results indicated that most of ore deposits are located at an active fault zone which is characterised by high seismic activity. There are high deformation zone trends NE-SW. There is a high value zone located approximately at the centre of the northern portion of the study area. This high energy zone is oriented towards NE and extends to the Red Sea. The energy map shows that the energy released from the study area is considered as a part of the energy release of the Red Sea area suggesting a tectonic connection between this region and the Red Sea.

Crustal deformation of the southeastern corner of Egypt derived from geodetic data

The proper evaluation of the crustal deformation is important prior to any strategic projects. Due to the importance of the southeastern corner of Egypt which contains many mineral resources beside a lot of attractive tourism places, we have selected this area to estimate the recent crustal movements and its relation to earthquake activities within this region using the available GPS and seismicity measurements. We used 19 permanent and campaign GPS sites in and around the study area that cover the time span 2007–2014. Most of these sites are related to Abu-Dabbab and Lake Nasser networks. The obtained GPS results show that there is an observed deformation in Abu-Dabbab area, along Red Sea coast, which characterized by a seismic cluster. The localization of the observed movements at Abu-Dabbab area may indicate that the deformation is related to a local structure within the study area. On the other hand, GPS sites located East of Lake Nasser and the permanent GPS sites in southern Egypt do not show any significant velocity field and it seems to be stable compared to Abu-Dabbab region. Even with the non-uniform spatial resolution of the GPS sites used in this work, our results are in good agreement with the seismicity of the study area.

A new tectonic model for Abu-Dabbab seismogenic zone (Eastern Desert, Egypt): evidence from field-structural, EMR and seismic data

Abu-Dabbab area is the most active seismic zone in the central Eastern Desert of Egypt, where seismic activities are daily recorded. The reported earthquakes are microearthquakes of local magnitudes (ML < 2.0). A spatial distribution of these microearthquakes shows that the earthquakes of the area follow an ENE–WSW trending pattern, which is nearly perpendicular to the Red Sea Rift. Focal mechanisms of different fault styles were recognized with dominant normal faulting (with a strike-slip component) events characterized by focal depths greater than 7 km and reverse ones of shallower focal depths. Several lines of evidence indicating that the brittle-ductile transition zone underlies the Abu-Dabbab area occurs at a relatively shallow depth (10–12 km) and it is acting as a low-angle normal shear zone (LANF). Field-structural, EMR and seismic data (this study) reveal that the maximum compressive stress (σ1) in the area is perturbed from the regional NW–SE direction to ENE–WSW orientation. This stress rotation is evidently akin to the reactivation of the crustal scale Najd Fault System (NFS), where such reactivation is attributed to the ongoing activity/opening of the Red Sea. Our tectonic model proposes that the continuous activity on the brittle-ductile transition zone including the LANF led to stress localization, which triggering a brittle deformation in the upper crustal-levels and associated shallow dipping thrusts. Such bimodal tectonic model suggests that the deep earthquakes are owing to the tectonic movement on the LANF (transtension), whereas the shallow earthquakes are related to a brittle deformation inside the fault blocks of the upper crust (transpression). Deformation creep along this zone didn’t permit continuous accumulation of strain and hence reduce the possible occurrence of large earthquakes.

Mapping b-values beneath Abu Dabbab from June to August 2004 earthquake swarm

Abu Dabbab area is considered as one of the most active earthquake sources in Egypt. It is defined by its swarm type activity, and complicated stress pattern. This study was conducted to evaluate the two and three dimensional spatial distribution of b-value at Abu Dabbab area (Margin of the northern Red Sea Rift, Egypt). The gridding technique of Wiemer and Wyss (1997) was used to compute b-value using ZMAP software. The b-value is calculated from a catalog consisting of 850 well-located earthquakes, which were recorded from 1st June to August 2004, using the maximum likelihood method. These earthquakes were recorded by temporary digital seismic network, with magnitudes ranging from −1 to 3.4ML. It is important to mention that the variations of b-value with time cannot be easily detected for a short period. Hence, this study has been carried out to examine the variations of b-value in space. The computed b-value in the Abu Dabbab area does not follow a uniform distribution. A small volume of anomalously high b-value (b>1.8) exists in the central part of the area at a depth between 6 and 9km. This seems to agree with the reported low velocity value derived from previous P-wave travel time tomography studies (Hosny et al., 2009) and the low Q value (Abdel-Fattah et al., 2008). The existence of an anomalously high b-value region may be attributed to the presence of a magma reservoir or dyke zone beneath the northern Red Sea Rift that causes an intensively heterogeneous fractured crust or unusually high pore pressure.

Quantitative Morphometric Analysis of Drainage Basins between Qusseir and Abu Dabbab Area, Red Sea Coast, Egypt using GIS and Remote Sensing Techniques

The coastal areas are considered of the promising areas for various types of sustainable development at present and in the future. As well as, this area occupies a large attention of the future planning for officials. The study area is located between Qusseir and Marsa Abu Dabbab along Red Sea coast. It is one of the most important areas. The study area is considered representing a promising and strategic target for urban and industrial expansions, as well as truism villages, but usually it is attacked by natural hazards, especially flash floods although rainfall is scarce in Eastern desert; it is well known for its flash floods with high velocity. The basin morphometric parameters, such as the linear, aerial and relief aspects of the basins, were determined using data (30 m resolution) from the ASTER DEM, Geographic Information System (GIS) and Remote-sensing data such as Landsat Thematic Mapper OLI. The study Linear, Relief and Arial aspects of drainage basins retrieved that, the area includes 25 basins, Wadi Ambagi basin is the largest basin in the study area (1538.24 km 2 ), while wadi Abu Sebekha is the smallest basin in the present study area (11.52 km 2 ). Primary results of this study were the determination that the basins have vast range stream order ranging from 3 rd to 7 th order drainage basins and a drainage pattern mainly of a parallel, dendritic, trellis and rectangular types. The observed drainage density in all basins range from 2.17 to 1.68 with an average is 1.86 km/km 2 . The average of elongation ratio (Re) for all the basins is 0.58, which mean that the most basins in the study area are elongated in shape but is relatively efficient in terms of the runoff discharge due to a large difference in slope. The bifurcation ratio ranges from 2.88 to 5.77, which indicates strong structural control of drainage patterns. Based on the slope map, it can be determined that the areas with high runoff and high erosion rates are those with steeper slopes. The area of rainwater accumulations and its close to mouths of wadis are more exposed to flash flooding. Based on the morphometric parameters which have a direct influence on flooding prone area, the flash flood hazard of sub-basins in the study area are classified into three groups; namely Extreme highly, moderately and Slightly hazard degree. However, most of the study area is environmentally nearly safe.

Crustal Structure in the Area of the Cannon Earthquakes of Abu Dabbab (Northern Red Sea, Egypt), from Seismic Tomography Inversion

Abstract Abu Dabbab seismogenic zone is located close to the Egyptian Red Sea coast. It is characterized by cannon earthquakes, long continued seismic activity, and frequent earthquake swarms. Earthquakes in this zone have occurred with high frequency over a long period of time in a confined linear zone that extends offshore in the Red Sea. A unique property is that earthquake signals can be heard by humans. Most previous studies suggested a magmatic origin for this activity. We perform a detailed earthquake tomography to image the crustal structure beneath Abu Dabbab and to explore the origin of its seismic activity and the cannon earthquakes. Based on the local and regional data, we construct a large‐scale seismic tomography model for the entire region and then enhance it for the local area of Abu Dabbab. We find the seismicity forms an arc‐shaped cluster that surrounds an aseismic block of high velocities and a low V P / V S ratio. According to the tomography results, we developed a new schematic geodynamic model proposing that the confined linear seismic zone in Abu Dabbab is due to the location of an active fault below a large, rigid, nondeformed block of Precambrian igneous rock, which reaches a depth of ∼10 km. The surface between this block and the moving parts of the fault are lubricated by fluids penetrating into the crust from the Red Sea as a result of combined strike‐slip and thrust displacements along the faults. These results reveal strong arguments for the tectonic origin of the seismicity associated with an important role of the fluid contents in Abu Dabbab area.

Using the HEM Technique and Its Relation to the Seismic Activity to Detect the Main Structural Setting and Rock Units at Abu-Dabbab Area, Egypt

Using the HEM Technique and Its Relation to the Seismic Activity to Detect the Main Structural Setting and Rock Units at Abu-Dabbab Area, Egypt

Seismicity, arrival time delays of the seismic phases and slowness characteristics study in Abu Dabbab area, Egypt

The temporal variations of seismicity from the Abu Dabbab area, 25km west of the Red Sea coast, are collected from the Egyptian national seismic network (ENSN), which has magnified the detection capability in that area to ML<1 earthquakes. These data show a sequence of the micro earthquake swarm during 2003–2011. This area has experienced larger shocks up to M=6 during the 20th century and its seismicity is concentrated in a narrow spatial volume.We analyze the digital waveform data of about 1000 seismograms, recorded by portable network of 10 vertical component seismographs that are employed in a temporary survey experiment in the Abu Dabbab area in 2004, and the results indicate: firstly, there are similar waveform seismograms, which are classified into three groups. In each group a master event is identified. Then, the arrival time delays of the P and S phases (Δtp and Δts, respectively) are measured between the master event and its slave events. Δtp and Δts range between −0.01 and 0.02s, respectively. These values are used to relocate the studied events. Secondly, the slowness vector (Δs) in 3-dimensional pattern, which is estimated using the genetic algorithms, is found Δsx=0.0153, Δsy=0.00093 and Δsz=0.2086s/km in the three spatial coordinates (X, Y and Z), respectively. These analyses demonstrate the inhomogeneities within the upper crust of the study area. Also, Δs shows little dependence of lateral distances and reasonably high slowness along the depth extent, which is consistent with the seismic velocity structure variations.

Preliminary crustal deformation model deduced from GPS and earthquakes’ data at Abu-Dabbab area, Eastern Desert, Egypt

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 3mm/yr, while the second block, moves to the SW direction of about 6mm/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 12km to about 1–2km 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 above the southern part of the study area. Based on the conducted source mechanism study, it is noticed that shallow earthquakes are associated by a high CLVD ratio (up to 40%). Furthermore, initiation of a high level seismic activity, without a large seismic main shock is observed in the Abu-Dabbab area. The distribution of micro-earthquakes tends to align in an ENE–WSW direction marking a zone of activity verse the Red Sea. The nucleation of the seismic activity beneath the southern part of the Abu-Dabbab crust is more consistent with the obtained crustal deformation result by increasing the crustal movement in the south part than the northern part. Then, based on the obtained results of the above mentioned studies; seismic tomography; source mechanisms, and crustal deformation we conclude that these seismic activities that are associated by crustal deformation are owing to some magma activity beneath the crust of the Abu-Dabbab area.

Comparative deformation analysis for Abu Dabbab area, Egypt

Abu-Dabbab area is characterized by high seismicity and complex tectonic setting, for these facts, a local geodetic network consisting of eleven 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 magnitude of the movements is distributed inhomogeneous over the area and it varies in average between 3 and 6 mm/yr. The results of the deformation analyses 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 NE-SW direction. The north and north-eastern 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 Abu-Dabbab area.

Source moment tensors of the earthquake swarm in Abu-Dabbab area, south-east Egypt

Seismic sources of a big swarm occurred in August 2004 have been studied by investigation of the moment tensors of 15 earthquakes with magnitudes range from 1.7 to 3.7. For each selected event, two sets of moment tensor inversions were carried out. The first one with fixed epicentral coordinates and the second one with variable epicentral coordinates. The data fit between observed and synthetic seismograms was computed for an elastic layered media, and minimized using a least squares algorithm. The obtained fault plane solution for each event is in agreement with the few reliable first arrival polarities. The resulting source time functions, characterized by one or two peaks, indicate that even small events might be associated with complex sources. The resulting focal mechanisms of the selected events represent different styles of faulting (normal and reverse with strike slip faulting mechanisms). The normal faulting events are characterized by focal depths larger than 7 km and the reverse ones are shallower with focal depths less than 6 km. A non-double-couple component, compensated linear-vector dipole (CLVD) ratio up to 35% is obtained for some events. The presence of some events with high CLVD ratio, besides the initiation of a high-level seismic activity, in the Abu-Dabbab area, without a large seismic main shock, led us to suggest that the August 2004 swarm might be due to igneous activity, increasing of fluid pressure and gases being consistent with the relatively high heat flow of the area.

Recent crustal deformation and seismicity studies at Abu-Dabbab area, Red Sea, Egypt

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.

Curie point depth beneath the Barramiya–Red Sea coast area estimated from spectral analysis of aeromagnetic data

The geothermal regime beneath the Barramiya–Red Sea coast area of the Central Eastern Desert of Egypt has been determined by using the Curie point depth, which is temperature dependent. This study is based on the analysis of aeromagnetic data. The depth to the tops and centroid of the magnetic anomalies are calculated by power spectrum method for the whole area. The result of this investigation indicates, two new maps of the Curie point depth (CPD) and the surface heat flow ( q) maps of the study area. The coastal regions are characterized by high heat flow (83.6 mW/m 2), due to the geothermic nature of the region, and shallow Curie depth (22.5 km), where (CPD) depends on the tectonic regime and morphology in the eastern part of the area. The western portion of the studied area has a lower heat flow (<50 mW/m 2) and deeper Curie depth (∼40 km), due to the existence of a large areal extent of negative Bouguer anomaly in the NE–SW direction. In addition to its bordering to the Red Sea margin, such high heat flow anomaly is associated with the increased earthquake swarms activity in the Abu Dabbab area.

Curie point depth beneath the Barramiya–Red Sea coast area estimated from aeromagnetic spectral analysis

The geothermal structure beneath of the Barramiya–Red Sea coast area of the Central Eastern Desert of Egypt has been determined using Curie point depth (CPD), which is temperature-dependent. The CPD and the surface heat flow (q) maps of such area are estimated by analyzing aeromagnetic data. Such data are low-pass-filtered and analyzed to estimate the magnetic bottom using the centroid method. The heat flow map reflects the geothermic nature of the region. However, it is suggested that the shallow Curie point temperature depth pattern depends on the tectonic regime and morphology, which continues eastwards through the Red Sea. Particularly, the coastal regions are characterized by high heat flow (83.6 mW/m2) and shallow Curie depth (22.5 km), whereas the western portion of the studied area has a lower heat flow (<50 mW/m2) and deeper Curie depth (~40 km). In addition to its bordering to the Red Sea margin, such high heat flow anomaly is associated with the increased earthquake swarms activity in the Abu Dabbab area. El-Hady (1993) attributed the swarm activity to the geothermal evolution. Also, the heat flow pattern is correlatable by the numerous results of shallow borehole temperature measurements as reported by Morgan and Swanberg (1979). A significant low heat flow extending in the northeast–southwest direction, which is associated with NE–SW large areal extent negative Bouguer gravity anomaly and NE/SW-trending belt of the deep CPD region, seems to be directly related to the surface outcrops of Precambrian older granitoids of the mountainous range of that trend.

Magma intrusion in the upper crust of the Abu Dabbab area, South East of Egypt from Vp and Vp/Vs tomography

3-Dimages of P-wave velocity and Vp/Vs ratio have been produced for the upper crust of the Abu Dabbab area, North Mars Alam city. The inversion of local travel times of high quality data recorded at eleven mobile seimic stations around the study area is carried out. The best, in the least-squares sense, 1-D Vp model and the average value of Vp/Vs (1.72) were computed as prerequisites of the 3-D inversion that reaches a depth of 14 km. From the 3-D model it is evident that the distributions of Vp and Vp/Vs are characterized by marked lateral and vertical variations delineating structural heterogeneities. Due to the presence of a thin layer of sedimentary rocks saturated with surface water, low P-wave velocity and high Vp/Vs values are noticed near the surface. At greater depths, high Vp and low Vp/Vs zones may indicate crustal rocks with relatively higher rigidity and brittle behavior, while high Vp/Vs and low Vp may identify zones of relatively softer rocks, with ductile behavior. Low P-wave velocity values are observed at the intersections among the faults. A possibility of some magma intrusion could be associated with the high Vp/Vs values which form an elongated anomaly, in the central part of the study area, which extends from a depth of 12 km to about 1–2 km of depth.

Exhumed fault scarps and drainage modification as proxies of neotectonics at the Abu Dabbab area, Eastern Desert, Egypt

The basement rocks, Neogene sediments and Quaternary alluvial deposits in the Abu Dabbab area, Eastern Desert of Egypt, are deformed by N-S, NE-SW, NW-SE and E-W trending faults. Complex cross-cutting relationships show a complicated history of initiation and reactivation of these faults. The recent fault scarps demonstrate different morphologies, modes of formation and relative ages. Recurrent, step and successively reactivated faulting was likely responsible for the exhumation and neo-formation of the fault scarps. Capture, deep incision, offset and reversal in flow direction of streams are the main drainage modifications induced by active faults. The concealed and active faults are associated with high drainage density anomalies. Segmentation phenomenon is common for all fault trends. Microearthquakes are concentrated at the intersection zones of faults and caused by upper crustal strike-slip, oblique-slip, reverse and normal faults. The paleostresses are not consistent with the present-day stress fields. The present-day NE-SW extension across the Red Sea combined with a local multidirectional tension led to reactivation of old faults and initiation of new fault trends.

Intrinsic and scattering attenuation in the crust of the Abu Dabbab area in the eastern desert of Egypt

Fifty-five microearthquakes recorded by a digital-temporary seismic network in the Abu Dabbab area in the Eastern Desert of Egypt were used to estimate the direct S-wave ( Q β), coda ( Q c), intrinsic ( Q i), and scattering quality factors ( Q s). Sato's [Sato H., 1977] single-scattering assumption was used to fit the amplitude envelopes of the coda at seven central frequency bands (1.5, 3, 6, 9, 12, 18, and 24 Hz), obtaining a Q c varying with frequency as generally observed in tectonically active areas. Lapse time dependence was also studied for the area, with the coda waves analyzed at window lengths ranging from 10 to 40 s starting from the onset of the S-wave arrival. The direct S-wave Q β was estimated using the coda normalization method [Aki, K., 1980a]. The frequency dependence of Q was investigated for the direct S-waves and coda waves. Results show a low quality factor and a high frequency parameter, indicating that the upper lithosphere of the Abu Dabbab area is seismically active and heterogeneous. Using the independent estimates of Q c and Q β, the intrinsic quality factor Q i was separated from the scattering quality factor. The results suggest that intrinsic dissipation plays a predominant role with respect to scattering phenomena in the area; the obtained Q values seem closer to those reported by analyzing volcano-tectonic earthquakes. This finding reflects that the cause of Abu Dabbab earthquake swarms might be igneous activity where the magma is ascending through joints or serpentinized joints that are dewatering.

Microearthquake studies in Egypt carried out by the geological survey of Egypt

Extensive microearthquake studies have been conducted in Egypt as a joint project between scientists from the Egyptian Geological Survey and Mining Authority (EGSMA) and U.S. scientists. At this stage, a great part of the data has been analyzed and two intensively active areas have been located: one in the Abu Dabbab area of the Eastern Desert, the second at the mouth of the Gulf of Suez near Gubal Island (Daggett et al., 1980). Both sites have been reported to be the epicenters of large earthquakes in 1955 and 1969, respectively. A few scattered earthquakes have also been located in the northern part of the Red Sea, some of which lie along its median axis (Daggett et al., 1986) adding to evidence for the medial opening of the northern Red Sea. After the occurrence of an earthquake (M = 5.5) in the Aswan region on 14 November 1981, continuous recording of the many aftershocks was carried out by EGSMA for about seven months from December 1981 to July 1982, when the temporary network was replaced by a network of telemetered seismographs installed and operated by Helwan Institute of Astronomy and Geophysics in cooperation with scientists from Lamont and Doherty Geological Observatory (LDGO). The majority of epicenters are concentrated in the vicinity of G. Marawa about 65 km upstream of Aswan Dam, along the E-W Kalabsha fault. The observed focal mechanism is consistent with a right-lateral strike-slip motion on the Kalabsha fault. Analysis of Aswan microearthquakes has been done by EGSMA in cooperation with scientists from California Division of Mines and Geology (CDMG).