National Research Institute Of Astronomy And Geophysics Research Articles

GPR and ERT Exploration in the Western Cemetery in Giza, Egypt

ABSTRACTA geophysical exploration employing ground‐penetrating radar (GPR) and electrical resistivity tomography (ERT) was conducted at the Western Cemetery, Giza, Egypt, in 2021–23 by a joint research team of Higashi Nippon International University, Tohoku University and the National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, Egypt. We believe we found an anomaly: a combination of a shallow structure connected to a deeper structure. The shallow structure, which is L‐shaped in the horizontal plane, 10 m by 10 m, was clearly imaged by GPR. It seems to have been filled with sand, which means it was backfilled after it was constructed. It may have been an entrance to the deeper structure. Its depth is of up to 2 m, measured from the ground surface. Below this structure, ERT reveals a highly electrically resistive anomaly, which extends over an area of about 10 m by 10 m. The depth of the structure is about 5–10 m below the surface. Electrically resistive material in a sand dune can be a mixture of sand and gravel, including sparse spacing or air voids within it. Neither GPR nor ERT could identify the properties of the anomaly.

Orbit Predictions for Space Object Tracked by Ground-Based Optical and SLR Stations

In many cases, we have few optical observations over a short time span, and most of the information generated is too limited to compute a full orbit according to the angles-only method. This study aims to develop a mathematical model to determine the precise orbit from the optical observation data by the least squares method. We have used a set of the Global Navigational Satellite Systems, which are tracked by the Optical Satellite Tracking Station (OSTS) at the National Research Institute of Astronomy and Geophysics (NRIAG), Egypt, to access high-quality predictions for the orbits. We analyzed the orbit predictions from the observations of these satellites that are tracked from seven world stations using the laser ranging method, and the obtained results are compared with orbital elements produced using the Two-Line Element (TLE). The results showed that the orbital prediction accuracy differs for optical observations from laser observations because of the inaccuracy of the NORAD catalog information used; this is due to the difference between the time of observation and the epoch time of TLE.

Magnitude of completeness for the Northern stations of the Egyptian National Seismological Network

After the occurrence of an earthquake near Cairo on October 1992 (Mw 5.8), the Egyptian authorities established the Egyptian National Seismological Network (ENSN), which was targeted to monitor the seismic activity in and around Egypt. The ENSN started operation in 1997 with 66 stations installed by the National Research Institute of Astronomy and Geophysics (NRIAG). Almost 55,000 events were recorded up until 2018 since the time of ENSN’s operation. After more than 20 years of establishing ENSN, a scientific project was funded to review the detectability of the stations by different methods; so, the goal of this research is to evaluate the magnitude of completeness (Mc) which represents an important parameter for instrumental catalog studies using different catalog-based methods. The Mc is calculated based on deflection from the linear relation of frequency-magnitude of the recorded events in ENSN’s catalog. Calculation of Mc is indispensable for knowing and clarifying the seismicity parameters such as the b value in the Gutenberg-Richter equation. Three different methods were used, i.e., maximum curvature method (MAXC), b value stability approach (MBS), and entire magnitude range method (EMR). The results determine the variations among different methods, up to 0.5 magnitudes unit is observed. The importance of this study comes from its concentrate on the detectability of ENSN’s stations to show their efficiency for recording seismic events with high accuracy and for contributing in evaluation of seismic hazard in Egypt, in seismic engineering applications to mitigate earthquake risk, and in changing the position of bad recording stations to a quieter place with minimum noise level.

First Optical Satellite Tracking Station (OSTS) at NRIAG-Egypt

In March 2019 the first dedicated of optical observation of space debris and artificial satellites (Optical Satellites Tracking Station (OSTS)) in Egypt has been performed by National Research Institute of Astronomy and Geophysics (NRIAG) at Kottamia Observatory. The 0.28 m Telescope is used for tracking and surveying debris and operational satellites at Low Earth Orbit (LEO), High ellipse orbit (HEO) and the Geosynchronous Earth Orbit (GEO). OSTS has also collaborated with International Scientific Optical Network (ISON) for optical observation. The necessary programs to control the telescope, camera and monitoring process are configured. Coordinate corrected metric data is provided with the time information. The system has validated and calibrated processing. The first results of the observations with image processing using Apex-2 software are presented. The optical observations using OSTS are being used to help characterize the debris environment in LEO, HEO and GEO to assist in the modeling projections for space debris database, real population and distribution, detection and orbital determination, and conjunction analysis between operational satellites and/or dangers debris.

A review of the Egyptian National Seismological Network after 20 years of operation

ABSTRACT On 12 October 1992, a moderate earthquake with magnitude, Mw 5.8 was occurred in Cairo; the epicentre is located 25 km south west of Cairo, resulted in great damage in the surrounding area and extended 300 km away from the epicentre. Subsequently, the government established Egyptian National Seismological Network (ENSN) under the supervision of National Research Institute of Astronomy and Geophysics (NRIAG) with 66 stations of different recording bands (e.g. short period, broadband) for monitoring the seismic activity in and around Egypt. The network started operation since mid-1997 up till now, consider revising 20 years of operation, a lot of changes were done (sensors, digitisers, station locations and even stations name), there is still the absence of adequate documentation of the type of changes made. This article is the first attempt to study the recorded data to track all changes done in the network, as a first step towards a different studies regarding determination of the detection capabilities of ENSN’s stations and proposed an optimisation solutions for the current faced problems. A software code was designed under Matlab programme to read around 55,000 recorded events and track different changes that took place during the operational time. The output of this study will affect all related research work including magnitude determination and hazard analysis.

Ambient Noise Level and Site Characterization in Northern Egypt

The characterization of the background seismic noise in any seismological network is an essential task for checking the performance of the recording stations. Hence, a funded project from Science and Technology Funding Authority (STDF) was awarded by the National Research Institute of Astronomy and Geophysics (NRIAG) in 2017 to detect the recording capabilities of the Egyptian National Seismological Network (ENSN), established after the Cairo Earthquake which occurred in Egypt on October 12, 1992. This article covers the first output of the project which shows the results of noise assessment for nine broadband stations located in northern Egypt. For a proper assessment of seismic data quality for a part of the ENSN network, the PASSCAL Quick Look Extended (PQLX) software was used, which is based on the calculation of power spectral density (PSD) and probability density function (PDF) for the background noise. The analysis covered almost one year of continuously recorded seismic data. The results show that some stations have very low detectability and higher noise level in some frequency bands which affects the recording of seismic events, while others show good performance. Complete site analysis for all stations was done to illustrate the present site response to be able to recommend whether to keep a station or to relocate it. To achieve this, the seismic noise data extracted from all stations of the considered zone was studied to determine the horizontal to vertical (H/V) spectral ratio method to study the amplification parameters of the recording site. The output of this study is useful for detecting operational problems in the northern part of the Egyptian seismological network and could be relevant for the reconfiguration and optimization of ENSN stations.

The Egyptian geomagnetic reference field to the Epoch, 2010.0

The present work is a compilation of two tasks within the frame of the project “Geomagnetic Survey & Detailed Geomagnetic Measurements within the Egyptian Territory” funded by the “Science and Technology Development Fund agency (STDF)”. The National Research Institute of Astronomy and Geophysics (NRIAG), has conducted a new extensive land geomagnetic survey that covers the whole Egyptian territory. The field measurements have been done at 3212 points along all the asphalted roads, defined tracks, and ill-defined tracks in Egypt; with total length of 11,586km. In the present work, the measurements cover for the first time new areas as: the southern eastern borders of Egypt including Halayeb and Shlatin, the Quattara depresion in the western desert, and the new roads between Farafra and Baharia oasis. Also marine geomagnetic survey have been applied for the first time in Naser lake.Misallat and Abu-Simble geomagnetic observatories have been used to reduce the field data to the Epoch 2010. During the field measurements, whenever possible, the old stations occupied by the previous observers have been re-occupied to determine the secular variations at these points.The geomagnetic anomaly maps, the normal geomagnetic field maps with their corresponding secular variation maps, the normal geomagnetic field equations of the geomagnetic elements (EGRF) and their corresponding secular variations equations, are outlined. The anomalous sites, as discovered from the anomaly maps are, only, mentioned. In addition, a correlation between the International Geomagnetic Reference Field (IGRF) 2010.0 and the Egyptian Geomagnetic Reference Field (EGRF) 2010 is indicated.

Estimating the magnitude of completeness for assessing the quality of earthquake catalogue of the ENSN, Egypt

After the Cairo Earthquake in 1992 with moderate magnitude (Ms 5.9), the government established the Egyptian National Seismological Network (ENSN) with 66 short-period and broadband stations, organized by National Research Institute of Astronomy and Geophysics (NRIAG). Around 55,000 local events were recorded from 1997 to 2014. The aim of this study is to assess the magnitude of completeness (M c) of an instrumental earthquake catalogue. Three different methods named the maximum curvature (MAXC), b value stability (MBS), and entire magnitude range (EMR) were applied to calculate M c and the results are compared together; all of these used methods are catalogue-based methods, in which M c is estimated based on departure from the linear frequency-magnitude relation of the local earthquakes published in the ENSN catalogue. Accurate knowledge of the magnitude of completeness M c is essential for many seismicity-based studies and particularly for mapping out seismicity parameters such as the b value of the Gutenberg-Richter relationship. The difference in M c between the three used methods is 0.9. However, tests performed on the diverse data sets presented here had confirmed that the EMR method is the more accurate method to estimate M c. Estimating M c solely based on the frequency-magnitude distribution (FMD) has some obvious drawbacks like the difficulty of estimating M c in areas of low seismicity. The final results showed that the MAXC technique (M c = 1.6 ± 0.02) needs fewer events to reach a stable result. While the MBS results (M c = 2.5 ± 0.04) gave always higher M c values compared with the other two methods, comparing to the third method, the EMR results (M c = 1.8 ± 0.03) maximize the amount of data available for the M c determination, which should serve to stabilize the M c estimates. This study will play an important role in the future reconfiguration of the ENSN stations.

Magnitude scales regression for Egyptian seismological network

After Cairo Earthquake in 1992 (Ms 5.9), the government established the Egyptian National Seismological Network (ENSN) organized by the National Research Institute of Astronomy and Geophysics (NRIAG) start to work since 1997; NRIAG has a real monitoring of the seismological activity in and around different parts of Egypt. A selected 5000 events from the ENSN annual bulletin in the period 2004–2013 with calculated local magnitude (ML) based on Richter regular formula was used in this study; a duration magnitude was calculated for these events and regressed with ML. Another aim of this study is to develop a regression relation of the calculated body wave magnitude (Mb) to the unified moment magnitude (Mw) which is the base for homogenization of earthquake catalogue needed for seismic hazard studies. Standard least square regression usually fails to give reliable results when both regressed variables have measurement errors; orthogonal standard regression (OSR) is the most reliable tool used for conversion of observed Mb values with the moment magnitude Mw. The accuracy of the resulting relations from regression have been checked with another 20 events of the data and shows the advantage of using OSR method to get regressed relation to homogenize any catalogue containing various magnitudes with measurement errors, by their regression with a Mw. The proposed procedure also remains valid in case the magnitudes have measurement errors different from unity.

A new velocity field from the analysis of the Egyptian Permanent GPS Network (EPGN)

For studying recent crustal movements and their relation to earthquake occurrence in large scales, the National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, Cairo, Egypt started in 2006 the establishment of the Egyptian Permanent GPS Network (EPGN). Beginning with 4 stations in 2007, 15 stations were operational at the end of 2011. In addition, a station in Alexandria of the French “Centre d'Etudes Alexandrines” (CEALX) was added as station to the EPGN. Nowadays, 16 stations are operational and an extension to 20 in the near future is expected. The collected EPGN data of the last 6 years are used in this work to throw light upon the present state of recent crustal movement of the whole of Egypt. Bernese software V. 5.0 was used for processing the collected data according to the IGS standards. In addition, selected IGS, AFREF, and EPN sites are processed for reference frame definition. In this first comprehensive analysis of the permanent network, a complete and consistent evaluation resulted in the first estimates of present day horizontal velocities and coordinate time series.

Influence of Solar Cycle Variations on Solar Spectral Radiation

The climatic changes associated with solar variability are largely caused by variations in total solar irradiance and solar spectral irradiance with solar activity. Thus the spectral composition of solar radiation is crucial in determining atomspheric structure. The variations in solar spectrum depend on the varied solar spots. Recently, evidence for a strong effect of solar activity on terrestrial isolation on ground-based measurements carried out by the National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, Egypt (lat. 29?52'N and long. 31?20'E) during (1990-2000) were presented. Specifically, a strong increase of terrestrial isolation with sunspot number as well as a decline of the solar spectrum with solar activity was reported. Daily measurements of the solar radiation between 280 nm and 2800 nm were made by Eppley Pyranometer and Pyrheliometer instruments. The decreasing at the range 280 - 530 nm and 530 - 630 nm are represented less than 50% of direct solar radiation and the stability of at the range 630 - 695 nm and 695 - 2800 nm it mean that; some of difference radiation is appear in diffused radiation which allow to height of the temperature as much as the largest associated with significance as it appears from the curves of relative humidity.

Interpretation of Geophysical Data at EL Fayoum—Dahshour Area, Egypt Using Three Dimensional Models

EL Fayoum–Cairo district lies in the north western part of Cairo city. It is affected by several earthquakes. According to the Egyptian Network Seismology of National Research Institute of Astronomy and Geophysics (NRIAG), the last one occurred in July 2005 with a magnitude of 4.2 in Richter scale. The Bouguer and the aeromagnetic anomaly data as well as the detailed land-magnetic survey have been subjected to different techniques of processing and interpretation to better understand the tectonic setting of the study area. For example, different kinds of filters such as 2D spectral analysis, 3D analytical signal, and Euler deconvolution techniques have been applied. Finally, the 2D modeling has been used to simulate the subsurface configuration along some selected profiles at the area. It can be noticed from the obtained results that, the seismic events (Dahshour earthquakes) are closely related to a major NNW normal fault which has a deep extension and slightly lateral displacement, in addition to its NE-conjugate faults. The recent seismic activities in the study area are directly related and/or associated with the rejuvenation of the lateral movements. Three-dimensional interpretations of the magnetic anomaly and Bouguer anomaly maps of Fayoum, Cairo province area, Northern Western Desert of Egypt have been presented. In addition, a high-resolution 3D magnetic and gravity model constrained with the seismic results reveals a possible crustal thickness and density distribution of the northern part of Egypt between the sedimentary cover and the mantel. The results reveal that the basement has an irregular surface with depths ranging from 3,600 to 5,500 m. Faults of the NNW, as well as ENE and NE directions have predominated and affected both the basement and the overlying sedimentary cover. Furthermore, the 2D modeling technique across long gravity and magnetic anomaly profiles have emphasized the basement topography and its overlying sedimentary section. The agreement between the results of gravity and magnetic surveys and geology on the other hand, confirm the reliability of the chosen constraints of interpretation.

Side pumping technique model for laser pumped by solar energy

A model of side pumping technique for a system of solar concentrators was performed for laser generation. Measurements for the total solar radiation in the hot desert area near Helwan which is south of Cairo by 30 km, of latitude 30°N and longitude 31°E were carried out. The instruments were installed on the rooftop of the National Research Institute of Astronomy and Geophysics (NRIAG). The measurements indicate that the annual average of the global solar radiation is 5·21 kWh/m2/day, direct solar radiation is 6·26 kWh/m2/day, diffuse solar radiation is 1·86 kWh/m2/day, the clearness index Kt is 0·61, and the diffuse fractionKD is 0·37. The performance of the laser rod and the performance of the system as a whole were tested. Finally, the measurements of solar radiation were applied to the model to obtain the behaviour of the laser output in different seasons, assuming that the concentrator system tracks the sun.

Spectral measurements of visible solar direct-normal irradiance and air pollutant attenuation coefficients at Helwan

Solar radiation spectra were measured by a ground-level pyrheliometer (Eppley NIP) equipped with a filter wheel. Three flat, circular, Schott filters were used to define three spectral bands. The filters were large band-pass filters of the types OG530, RG630 and RG695. The experiment was conducted from June 1991 to May 1992 on the roof of the new building of the National Research Institute of Astronomy and Geophysics (NRIAG) at Helwan. The Linke turbidity factor for the integrated radiation, and the spectral attentuation coefficients of solar energy caused by aerosols were computed. In comparison with earlier measurements in 1910, 1967 and 1987, it is clear that there is a continuous increase in the turbidity factor, due to an increase of industrial waste in the Helwan atmosphere. A correlation analysis between the turbidity factors and the total suspended particles, smoke and sulphur dioxide was carried out. Meteorological elements and sand storms have been taken into consideration in the correlation analysis.