Hakim Saibi

Principal component, chemical, bacteriological, and isotopic analyses of Oued-Souf groundwaters (revised)

AbstractOued-Souf City, located in the northwestern part of Algeria, has rapidly grown and been urbanized. The city and surrounding areas depend heavily on groundwater as a water source for drinking, as well as domestic, industrial, and agricultural uses. Comprehensively understanding the chemistry of the groundwater provides insight into the interaction of water with the environment and contributes to better overall resource management. The phreatic groundwaters are SO4–Ca in character. These waters are hard with a high salinity, which poses a distinct danger for plants. Furthermore, major chemical elements in the water have concentrations above the values recommended by World Health Organization. The phreatic groundwaters display bacteriological germs in sampled waters, and high concentrations of nitrates were detected in the samples due to the absence of a formal sanitation network. In this work, stable and radioactive isotopes are used to understand the water origin of the phreatic groundwaters. The present isotopic study suggests that the groundwaters from the Oued-Souf phreatic aquifer are composed of two primary components, one from infiltrating recent rain waters and the other one from deep captive groundwaters. Herein, descriptive statistics, correlation matrices, and factor analyses were employed to understand the hydrochemistry of the groundwater in the phreatic aquifer in the Oued-Souf area.

Integrated gradient interpretation techniques for 2D and 3D gravity data interpretation

The Obama geothermal field is located on the western part of Kyushu Island, Japan. This area has importance due to its high geothermal content which attracts sporadic researchers for study. In 2003 and 2004, Obama was covered by gravity surveys to monitor and evaluate the geothermal field. In this paper, the surveyed gravity data will be used in order to delineate and model the subsurface structure of the study area. Gradient methods such as analytic signal and vertical derivatives were applied to the gravity data. The available borehole data and the results of the gradient interpretation techniques were used to model the Obama geothermal field. In general, the obtained results show that the gradient interpretation techniques are useful to obtain geologic information from gravity data.

Analysis and interpretation of gravity data from the Aluto-Langano geothermal field of Ethiopia

The Aluto-Langano geothermal field is located in the central southern portion of Ethiopia within the Ethiopian Rift Valley. The gravity of the area was surveyed in an attempt to delineate the subsurface structure and to better understand the relationship between the geothermal systems and the subsurface structure. The gravity data were analyzed using integrated gradient interpretation techniques, such as the Horizontal Gradient (HG), Source Edge Detection (SED), and Euler Deconvolution (ED) methods. These techniques detected many faults that were compared with the mapped faults in the surface geology. The results of the present study will lead to an improved understanding of the geothermal system in the study area and aid the future geothermal exploration of the area.

Integrating potential fields with remote sensing data for geological investigations in the Eljufra area of Libya

In this study, we successfully integrated geological data, potential field data, and remote sensing data with the aim of investigating and improving our knowledge of the structural setting of the Eljufra area, northwestern Libya. SPOT-5 panchromatic band and digital elevation models (DEM) were used to construct surface shaded maps, and gravity and aeromagnetic surveys were used to provide information on subsurface structures and the nature of intrusive bodies. The results revealed that the prevailing trend of lineaments is NNW-SSE and NNE-SSW. A Bouguer anomaly map revealed that horst and graben blocks occur inside the large graben. An analytic signal method was applied to the aeromagnetic data to estimate locations and the minimum depths to the contact. A comparison of gravity and magnetic data provided information on hydrothermally altered basalt and sediment density. An anticlinal structure was detected in the western part of the study area. The effects of faults on basalt rocks indicated geological time for volcanic activity.

Integrating data from remote sensing, geology and gravity for geological investigation in the Tarhunah area, Northwest Libya

Abstract The present work deals with the integration of remote-sensing, surface-geology and gravity-survey data to improve the structural knowledge of the Tarhunah area, northwest Libya. Geological information and remote-sensing data provided information about the surface structure. A gravity survey was conducted to decipher the subsurface structure. The results revealed that a basin having a width of 39 to 48 km trends NE. A two-dimensional (2-D) schematic model shows that the basin gradually deepens toward the southwest. Faults determined from a horizontal gradient, tilt derivative, and Euler deconvolution show a depth range of 2.5 to 7.5 km. The integration and interpretation of the results indicate that volcanic activity was related to the tectonic activity of an anticlinal structure called the Jabal Uplift.

Geochemical and stable isotopic studies of Gulf of Suez’s hot springs,Egypt

The Gulf of Suez region is one of the most interesting geothermal areas in Egypt because of the high temperatures of its springs. The eastern and western shores of the Gulf of Suez are characterized by superficial thermal manifestations including a cluster of hot springs with varied temperatures. Variations of deuterium and oxygen-18 concentrations in thermal waters have been used to aid in describing the source of recharge in the Gulf of Suez hot springs. Isotope and geochemical data for the Gulf of Suez thermal waters suggest that recharge to the hot springs may not be entirely from the Gulf of Suez water, but possibly from the meteoric water that comes from areas of higher altitude surrounding the hot springs.

Relation between structure and low-temperature geothermal systems in Fukuoka city, southwestern Japan

The Fukuoka area is located in the southwestern part of Japan. The Yokote-Ijiri area, located in the southern part of Fukuoka city, has several low-temperature geothermal systems, including eleven hot springs. From 1996 to 2008, the Fukuoka area was investigated by gravity survey, using Scintrex CG-3 and CG-3M gravimeters, in an attempt to delineate its subsurface structure. The surveys were intended to improve the understanding of the relation between the geothermal systems and the subsurface structure as well as to locate the active faults in the surveyed area, which are responsible for generating large earthquakes. The gravity data were analyzed using integrated gradient interpretation techniques, such as the Horizontal Gradient (HG), Tilt Derivative (TDR), and Euler deconvolution methods. With these techniques, many faults were detected, including the famous Kego fault, which is an active fault in Fukuoka city. A 2-D gravity model was constructed to show the relationship between the faults and the geothermal systems. The results of the present study will hopefully lead to an understanding of the relationships between the interpreted faults and the location of the low-temperature geothermal systems and possibly aid in future geothermal exploration of the area.

Structural Investigations of Afghanistan Deduced from Remote Sensing and Potential Field Data

This study integrates potential gravity and magnetic field data with remotely sensed images and geological data in an effort to understand the subsurface major geological structures in Afghanistan. Integrated analysis of Landsat SRTM data was applied for extraction of geological lineaments. The potential field data were analyzed using gradient interpretation techniques, such as analytic signal (AS), tilt derivative (TDR), horizontal gradient of the tilt derivative (HG-TDR), Euler Deconvolution (ED) and power spectrum methods, and results were correlated with known geological structures.The analysis of remote sensing data and potential field data reveals the regional geological structural characteristics of Afghanistan. The power spectrum analysis of magnetic and gravity data suggests shallow basement rocks at around 1 to 1.5 km depth. The results of TDR of potential field data are in agreement with the location of the major regional fault structures and also the location of the basins and swells, except in the Helmand region (SW Afghanistan) where many high potential field anomalies are observed and attributed to batholiths and near-surface volcanic rocks intrusions.A high-resolution airborne geophysical survey in the data sparse region of eastern Afghanistan is recommended in order to have a complete image of the potential field anomalies.

Integrating Gravity Data With Remotely Sensed Data for Structural Investigation of the Aynak-Logar Valley, Eastern Afghanistan, and the Surrounding Area

This study integrates gravity data with interpreted lineaments from remotely sensed images and geological fault in an effort to understand the geological structure of the Aynak-Logar Valley (ALV) and its surrounding area in eastern Afghanistan. Integrated analysis of Landsat Enhanced Thematic Mapper Plus (ETM+), Shuttle Radar Topography Mission (SRTM), and Digital Elevation Model (DEM) data was applied for lithological mapping and extraction of geological lineaments and landforms. Gravity data were used to delineate a detailed picture of the subsurface structure. Several gravity interpretation techniques such as horizontal gradient (HG), tilt derivative (TD), and analytic signal (AS) were applied to the gravity data with the objective of making geological features such as faults and contacts more visible, and also a three-dimensional (3-D) inversion model of gravity data was developed to show the density distributions in the study area. The combination of these geoscience data provides information about the subsurface structure of ALV. The interpreted faults from remote sensing are striking NE-SW. The faults and contacts from geological map and gravity data analysis are striking mainly in NNE-SSW, which is the direction of the Kabul block trending fault structure.

3D Gravity Inversion using Tikhonov Regularization

Subsalt exploration for oil and gas is attractive in regions where 3D seismic depth-migration to recover the geometry of a salt base is difficult. Additional information to reduce the ambiguity in seismic images would be beneficial. Gravity data often serve these purposes in the petroleum industry. In this paper, the authors present an algorithm for a gravity inversion based on Tikhonov regularization and an automatically regularized solution process. They examined the 3D Euler deconvolution to extract the best anomaly source depth as a priori information to invert the gravity data and provided a synthetic example. Finally, they applied the gravity inversion to recently obtained gravity data from the Bandar Charak (Hormozgan, Iran) to identify its subsurface density structure. Their model showed the 3D shape of salt dome in this region.