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1

Alternative vertical electrical sounding technique for hydraulic parameters estimation of the quaternary basaltic aquifer in Deir Al Adas area, Yarmouk Basin, Southern Syria

Asfahani J., Al-Fares W.

Acta Geophysica

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2021

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Vol. 69, no. 5

1901--1918

EN

An alternative geoelectrical approach, based on using the technique of vertical electrical sounding (VES), is developed and proposed to estimate the hydraulic conductivity and transmissivity parameters of the quaternary fractured basalt aquifer (B1Q1) in Deir Al-Adas region, Southern Syria. Nineteen VES points were executed by Schlumberger configuration, where three of them were made near the available boreholes for comparison. Hydraulic conductivity and transmissivity aquifer parameters are obtained by analyzing conjointly the available pumping test results from the existing boreholes and the electrical Dar-Zarrouk (R) parameters from VES data. An empirical equation between the transverse resistance (R), resulting from VES interpretation, and hydraulic conductivity determined from pumping test is established to estimate geophysically hydraulic conductivity of the Quaternary basalt aquifer. A closed agreement is obtained between the computed hydraulic conductivity and the one determined from pumping test. The established calibrated relationship is consequently used to extrapolate and estimate the transmissivity and the hydraulic conductivity parameters in all VES points, where geoelectrical measurements have been carried out. This extrapolation allows characterizing and deriving the spatial maps of hydraulic conductivity, transmissivity and other related hydrogeophysical parameters in the study area. The integrated acquired results give insights, particularly on the groundwater potentiality of the study region, direction of groundwater flux, and plausible lava directions flux. The resulting maps are important in future modeling processes oriented towards better exploiting of the aquifers. The proposed alternative technique is successfully applied in the study area and can be therefore applied for studying similar basaltic environments worldwide.

2

Porosity and hydraulic conductivity estimation of the basaltic aquifer in Southern Syria by using nuclear and electrical well logging techniques

Asfahani J.

Acta Geophysica

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2017

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Vol. 65, no. 4

765--775

EN

An alternative approach using nuclear neutron-porosity and electrical resistivity well logging of long (64 inch) and short (16 inch) normal techniques is proposed to estimate the porosity and the hydraulic conductivity (K) of the basaltic aquifers in Southern Syria. This method is applied on the available logs of Kodana well in Southern Syria. It has been found that the obtained K value by applying this technique seems to be reasonable and comparable with the hydraulic conductivity value of 3.09 m/day obtained by the pumping test carried out at Kodana well. The proposed alternative well logging methodology seems as promising and could be practiced in the basaltic environments for the estimation of hydraulic conductivity parameter. However, more detailed researches are still required to make this proposed technique very performed in basaltic environments.

3

Geoelectrical and hydrochemical investigations for characterizing the salt water intrusion in the Khanasser valley, northern Syria

Asfahani J., Abou Zakhem B.

Acta Geophysica

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2013

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Vol. 61, no. 2

422--444

EN

An integrated approach of geoel ectrical and hydrochemical investi- gation surveys was proposed for indicating contact regions between saline and fresh groundwater in the Khanasser valley region, northern Syria. The qualitative and quantitative interpretations of 34 vertical electrical soundings (VES) enable to characterize the salt water intrusion laterally and vertically. The established iso-apparent resistivity maps for different AB/2 spacings obviously indicate the presence of a low-resistivity (less than 4 Ohmźm) zone related to the salt water intrusion in the Quaternary and Paleogene deposits. The different hydrochemical and geophysical parameters, such as electrical resistivity, total dissolved solids (TDS) and major ions concentrations used to characterize the salt water intrusion gave almost similar results in locating and mapping the different boundaries of the groundwater salinity. The proposed approach is useful for mapping the interface be tween different groundwater quali- ties, and can be therefore used to successfully characterize the salt water intrusion phenomenon in other semi-arid regions. The application of such an approach is a powerful tool and can be used for water resource management in the water scarce areas.

4

Evaluation of earthquake activity along the Serghaya fault, Syria, from instrumental seismic data

Asfahani J., Abdul-Wahed M.K.

Acta Geophysica

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2013

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Vol. 61, no. 1

37--59

EN

This is a tentative study in order to characterize and identify the Serghaya fault in Syria through an analysis of its instrumentally observed earthquake activity for the period of 1 995-2009. Different approaches are used to evaluate a - and b -values of the Gutenberg–Richter relation. It has been found that the computed b -values (around 1.5) are bigger than usually expected, which could be related either to incompleteness of earthquake catalogue or to invalidity of the Gutenberg–Richter model in the case of Serghaya fault. Based on several explanations of high b-values, existing in the literature, it can be inferred that the events recorded on the Serghaya fault occurred at small depths in the heterogeneous milieus under low stresses. A relative seismic quiescence from 1900 up to now is observed, whereas the biggest earthquake recorded during the study period does not exceed magnitude 3.9. Such quiescence does not reflect accurately an earthquake potential of the Serghaya fault and can probably indicate a large-magnitude earthquake occurrence in near future. The established earthquake catalogue must be necessarily completed in order to deeper characterize the real behavior of the Serghaya fault. Such a characterization, accompanied with seismic activity evaluation, could be used in the assessment of seismic hazard.

5

Quaternary aquifer transmissivity derived from vertical electrical sounding measurements in the semi-arid Khanasser Valley Region, Syria

Asfahani J.

Acta Geophysica

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2012

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Vol. 60, no. 4

1143-1158

EN

Vertical electrical sounding technique (VES) is used as an alternative approach to pumping test for computing the Quaternary aquifer transmissivity in the Khanasser Valley, Northern Syria. The method is inexpensive, easy and gives faster results with higher special resolution than the traditional pumping technique. The hydraulic conductivity values obtained using VES agree with the pumping test results, which in the Khanasser Valley vary between the order of 0.864 and 8.64 m/day (10–5 and 10–4 m/s). The probable location of the Quaternary aquifer in the Khanasser Valley is obtained through the transmissivity map derived from VES. The knowledge of transmissivity is fundamental for modeling and management processes in the Khanasser Valley. Other similar semiarid regions can benefit from the approach successfully applied in the study area.

6

Electrical resistivity investigations for guiding and controlling fresh water well drilling in semi-arid region in Khanasser Valley, Northern Syria

Asfahani J.

Acta Geophysica

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2011

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Vol. 59, no. 1

139-154

EN

Electrical resistivity survey is conducted in the Khanasser Valley, considered as a semi-arid region in Northern Syria, to guide and control fresh water well drilling. Vertical Electrical Soundings (VES) are carried out near the existing wells, which were also used to measure salinity and conductivity of water samplings. Resistivity and hydrogeological data combination made it possible to establish empirical relationships between earth resistivity, water resistivity, and the amount of total dissolved solids (TDS). These relationships are used in the present research in order to follow the TDS salinity variations, both in lateral and depth directions, along the longitudinal profile LP3, located in Khanasser Valley. Apparent salinity map under this profile is established for Quaternary and Paleogene deposits, and boundaries of suitable areas for fresh water well drilling in the totality of the Khanasser Valley are drawn. It was shown that excessive fresh-water depletion may affect the groundwater quality by upward seepage of saline water. Therefore, it is important to keep the fresh-salt water interface in a stationary situation. The geoelectrical methods widely contribute in determining the position of such interface, and can be easily applied in similar arid areas.

7

A combined methodology of multiplet and composite focal mechanism techniques for identifying seismologically active zones in Syria

Abdul-Wahed M.K., Asfahani J., Al-Tahhan I.

Acta Geophysica

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2011

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Vol. 59, no. 5

967-992

EN

This contribution is an attempt to enlarge the current knowledge about the focal mechanisms as well as the seismotectonic settings in Syria. The seismologically active zones have been identified by applying an appropriate methodology to the events recorded during the period 1995-2003 by the Syrian National Seismological Network (SNSN). The recorded events in Syria were classified as weak during the research period. It was extremely important to propose and apply an appropriate methodology to identify the focal mechanisms generating this seismic activity. The proposed methodology consists of applying a combination of two techniques: the multiplet and the composite focal mechanisms. The combination of many events in one composite focal mechanism was realized by a multiplet technique using the spectral coherence of the events as a measure of similarity. The application of the proposed methodology allows a data set of composite fault plane solutions to be obtained. Most of the composite fault plane solutions had strike-slip mechanisms which are in agreement with the configuration of seismogenic belts in Syria.