Mohamed Rashed

Red Sea rifting controls on aquifer distribution: Constraints from geochemical, geophysical, and remote sensing data

Highly productive wells in the Central Eastern Desert of Egypt are tapping groundwater in subsided blocks of Jurassic to Cretaceous sandstone (Taref Formation of the Nubian Sandstone Group) and Oligocene to Miocene sandstone (Nakheil Formation), now occurring beneath the Red Sea coastal plain and within the proximal basement complex. Aquifer development is related to Red Sea rifting: (1) rifting was accommodated by vertical extensional displacement on preexisting NW-SE– to N-S–trending faults forming a complex array of half-grabens and asymmetric horsts; and (2) subsided blocks escaped erosion accompanying the Red Sea–related uplift. Subsided blocks were identifi ed and verifi ed using satellite data, geologic maps, and fi eld and geophysical investigations. Interpretations of very low frequency (VLF) measurements suggest the faults acted as conduits for ascending groundwater from the subsided aquifers. Stable isotopic compositions (δD: –19.3‰ to –53.9‰; δ 18 O: –2.7‰ to –7.1‰) of groundwater samples from these aquifers are interpreted as mixtures of fossil (up to 70%) and modern (up to 65%) precipitation. Groundwater volumes in subsided blocks are large; within the Central Eastern Desert basement complex alone, they are estimated at 3 × 10 9 m 3 and 10 × 10 9 m 3 for the

Smart stacking: A new CMP stacking technique for seismic data

This article describes a new common-midpoint stacking method for seismic data, called “smart stacking,” which has been tested using synthetic PSTT and high-resolution shallow data. This method is based solely on optimizing seismic amplitudes of the stacked signal by excluding harmful samples from the stack and applying more weight to the central part of the samples population.

Fifty years of stacking

Common-Mid-Point (CMP) stacking is a major process to enhance signal-to-noise ratio in seismic data. Since its appearance fifty years ago, CMP stacking has gone through different phases of prosperity and negligence within the geophysical community. During those times, CMP stacking developed from a simple process of averaging into a sophisticated process that involves complicated mathematics and state-of-the-art computation. This article summarizes the basic principles, assumptions, and violations related to the CMP stacking technique, presents a historical overview on the development stages of CMP stacking, and discusses its future potentiality.

On the application of GPR for locating underground utilities in urban areas

With the rapid growth of complex network of different types of underground utility under large cities, the need of a noninvasive technique capable of swiftly and precisely detecting these utilities in such a noisy urban environment increases. Ground-penetrating radar (GPR) is considered one of the most promising techniques in this field. This study presents the experience of GPR data acquisition, processing, and interpretation in three cities located along the coast of the Red Sea. These cities are Jeddah in Saudi Arabia and Sharm El-Sheikh and Qusier in Egypt. Data acquisition parameters varied in the three cities based on site conditions, target characteristics, and equipment availability. The processing flows were kept simple to avoid introducing artifacts to the collected data. The results show that despite the difference in site conditions and survey parameters among the three cities, with the exception of fiber optic cable, GPR technique is capable of detecting different kinds of underground utilities and precisely determine the extension, diameter, and depth of burial of these utilities.

Mapping underground utilities within conductive soil using multi-frequency electromagnetic induction and ground penetrating radar

The incessant expansion of megacities is usually associated with the extension of different underground utilities underneath these cities. In recent years, the need for a swift, precise, cost-effective, and environmentally benign tool to map these utilities in such a harsh urban environment is becoming a necessity. In coastal cities, such as Jeddah City in Saudi Arabia, cultural noise, the shallow water table, and the conductive nature of soil form additional obstacles to a successful mapping of underground utilities. This study presents the experience of applying a combined electromagnetic induction and ground penetrating radar surveys over a test site in Jeddah City in order to assess the capability of the suggested combination to map different kinds of underground utilities in such an environment. The results show that the suggested combination can be an efficient tool to map different underground utilities buried within conductive soil, and it provides valuable information about objects’ depth, shape, and dimensions.

Integrated solutions for hydrologic investigations in arid lands

Hydrological assessment studies across vast regions of the arid world are often hindered by the inaccessibility of these areas and the paucity of data sets, as well as the high expenses and diffi culties entailed in acquiring these data sets, their unpublished nature, and their varying scales, projections, and datum. Using the Eastern Desert (ED) of Egypt (225,000 km 2 ) and the Sinai Peninsula (61,000 km 2 ) as test sites, we demonstrate practical and cost-effective integrated (geochemistry, geophysics, and modeling) solutions that utilize web-based geographic information system (GIS) (http://www.esrs .wmich.edu/webmap) technologies and take advantage of readily available global remote sensing data sets. Adopted methodologies allowed: (1) development of conceptual models for hydrogeologic settings conducive to groundwater entrapment and augmentation, including groundwater in fractured basement aquifers, groundwater impounded by dike swarms crosscutting alluvial aquifers, and groundwater residing in alluvial aquifers associated with ascending deep-seated fossil waters; (2) selection of criteria to identify and validate the preferred distribution of each of these aquifer types and usage of the selected criteria and observations from the GIS data sets to identify, test, and refi ne potential well locations; and (3) construction and calibration of hydrologic models to estimate average annual recharge over the major watersheds in the Sinai (463 ◊ 10 6 m 3 /yr) and ED (171 ◊ 10 6 m 3 /yr) and the average modern contributions to Nubian fossil aquifers (Sinai: 13 ◊ 10 6 m 3 /yr), and to model the partitioning of precipitation as a function of precipitation amounts. The successful application of the integrated and cost-effective methodologies developed for the study areas should invite similar applications in arid regions elsewhere.

Double-Sided Sliding-Paraboloid (DSSP)

Background noise in Ground Penetrating Radar (GPR) data is a nagging problem that degrades the quality of GPR images and increases their ambiguity. There are several methods adopting different strategies to remove background noise. In this study, we present the Double-Sided Sliding-Paraboloid (DSSP) as a new background removal technique. Experiments conducted on field GPR data show that the proposed DSSP technique has several advantages over existing background removal techniques. DSSP removes background noise more efficiently while preserving first arrivals and other strong horizontal reflections. Moreover, DSSP introduces no artifacts to GPR data and corrects data for DC-shift and wow noise. Display Omitted We propose a novel method for background noise removal in GPR data.The proposed method, named DSSP, is an extension of the rolling ball algorithm.DSSP method has several advantages in removing the background noise.Field GPR data are used for evaluation and indicate image quality improvement.

Adaptive boxcar background filtering for real-time GPR utility detection

Ground Penetrating Radar (GPR) investigation tools are increasingly used for real-time detection of underground utilities. Background noise is an annoying problem, because it sometimes masks the reflection from objects of interest. This study introduces an efficient background removal algorithm, which is so simple that it can be incorporated into GPR logging devices. The algorithm is based on the recently published outliers-out algorithm for stacking seismic data. Experiments conducted on both synthetic and field GPR data show that proposed background removal algorithm yields much better results than the commonly used average trace subtraction algorithm in a relatively comparable computational time.