Abdallah Al Zoubi - Academia.edu (original) (raw)
Papers by Abdallah Al Zoubi
Environmental Earth Sciences, 2021
The presence of buried salt layer in the Ghor Al-Haditha area is discussed concerning sinkhole ha... more The presence of buried salt layer in the Ghor Al-Haditha area is discussed concerning sinkhole hazard. Numerous geophysical methods such as seismic refraction (SRFR), reflection (SRFL), seismic tomography, multichannel analysis of surface waves (MASW) were developed earlier for the salt layer identification. Geophysical criteria of salt parameters (such as longitudinal Vp and shear Vs wave velocities) were established to identify salt layers. This paper presents new geophysical results proving the salt extension in the Dead Sea (DS) coastal area in its eastern shore potentially representing a sinkhole hazard. The reprocessing technique of MASW data using the synthetic modeling enabled us to detect salt layer characteristics such as depth to its top, the thickness of the layer, and its Vs velocity. It was established that a salt layer with 7–10 m thick is located at a depth of 37–41 m and is characterized by shear-wave velocity (Vs) of 850–1200 m/s. Similar results were obtained by the Transient Electromagnetic (TEM) resistivity method, which detected a comparatively resistive salt layer at a background of very low resistivity. The resolution of the TEM method allows detecting a salt layer of 3 m thick and more at a depth of 39–40 m. Seismic refraction data processing has shown the presence of a salt layer with a velocity of more than 2900 m/s at approximately or the same depths. Analysis of seismic tomography data also confirms the parameters of the discovered target. Analysis of results of geophysical studies in the western and eastern DS shores, comparison of geological conditions in shores, and sinkhole development, enabled us to conclude with a high probability that salt layers exist in both shores and sinkhole development is determined here by similar mechanisms.
Near Surface 2005 - 11th European Meeting of Environmental and Engineering Geophysics, 2005
P078 SINKHOLE HAZARD ASSESMENT IN THE DEAD SEA AREA – TWO GEOPHYSICAL ASPECTS OF THE PROBLEM 1 Su... more P078 SINKHOLE HAZARD ASSESMENT IN THE DEAD SEA AREA – TWO GEOPHYSICAL ASPECTS OF THE PROBLEM 1 Summary A combination of different surface geophysical techniques is used as a tool for sinkhole development prediction. While each of the geophysical methods alone does not in general facilitate reliable detection of subsurface voids the combination of different geophysical methods does allow us to detect (1) the dissolution caves within the salt unit (Microgravity and Seismic Diffraction); (2) the depth to the water table (MRS) and (3) distribution of the bulk resistivity (related to salinity) over the space (TEM and CVES) with greater
ABSTRACT We consider a new approach to use the geoelectric methods for studying the both uppermos... more ABSTRACT We consider a new approach to use the geoelectric methods for studying the both uppermost part of section and salt layer conditions in the sinkhole development sites. The Electric Resistivity Tomography (ERT) is used here to detect shallow deformations in subsurface sediments. Resistivity prospecting yields information about both lateral and vertical distribution of resistivity through the geological section and can therefore be used in both qualitative and quantitative ways for the identification of structure and features at shallow depths. As it follows from the modified Archie's Law, resistivity of the unsaturated sediments is determined by their porosity. The higher the porosity, the higher is the resistivity. It will also depend on volume of the electrolyte in pores and resistivity of the fluid . Note that after mechanical models available the higher porosity in sinkhole development sites is caused by the void presence at depth. 2D and 3D mapping was carried out in the Mineral Beach area in Israel and in the Ghor Al-Haditha site in Jordan. ERT method shown high resistivity anomaly of some thousands Ohm-m located along the salt edge. The Transient Electromagnetic Method (TEM) also referred to as the Time Domain Electromagnetic Method (TDEM) is sensitive to the bulk resistivity (conductivity) of the studied medium, especially in the low-resistivity range. Transient Electromagnetic (TEM) method in its FAST modification was used for studying the salt layer conditions (salt porosity, depth of the salt top and thickness of the salt layer) and distribution of bulk resistivity in vicinity of the salt border (to resolve the problem of water salinity). The methodology includes numerous measurements through the sinkhole development areas. Earlier the TEM method was used extensively worldwide for locating the fresh-saline water interface in coastal areas and for estimating groundwater salinity. In our study we have mapped salt layer geometrical parameters (e.g. depth to salt top, salt layer thickness) as well as salt resistivity that is measure of salt porosity. New methodology permits also 2D and 3D presentation of the acquired results in spite methodology itself of the data acquisition is of 1D in its origin. Acknowledgements This study has been supported by the USAID MERC Program M27-050
Journal of Environmental and Engineering Geophysics, 2000
A DC resistivity profiling experiment was conducted over a buried cavity using a SYSCAL-R2 resist... more A DC resistivity profiling experiment was conducted over a buried cavity using a SYSCAL-R2 resistivity instrument at the location of a proposed highway at the Ras en Naqab escarpment, Aqaba Province, southwest Jordan. The objective of the study was to evaluate the resolution of the resistivity technique in detecting and locating significant anomalies (high resistivity) over underground cavities. Resistivity profiling measurements were carried out utilizing the following arrays: (1) Alpha-Wenner; (2) Beta-Wenner; (3) Gamma-Wenner; (4) Pole-Pole; (5) Combined Head-on. Results of the survey demonstrated a strong correlation between resistivity anomalies and a subsurface void. An open and air-filled cavity exhibits markedly high-resistivity anomalies. In addition, the survey indicated that caverns with diameters as small as [Formula: see text] can be detected at shallow depths below surface and can be positioned using the resistivity profiling method. Correlations between field results ...
GEOPHYSICS, 2008
Magnetic resonance sounding (MRS) is a geophysical technique developed for groundwater exploratio... more Magnetic resonance sounding (MRS) is a geophysical technique developed for groundwater exploration. This technique can be used for investigating karst aquifers. Generally, the study of a karst requires a 3D field setup and corresponding multichannel data-acquisition instruments. Now only single-channel MRS equipment is available; i.e., the time needed for a 3D MRS field survey is multiplied by a factor of four or five. Where karst caverns are natural hazards, as in the Dead Sea coastal area at Nahal Hever, Israel, even an approximate localization of potentially dangerous zones and a corresponding estimation of the hazard dimensions are useful. We studied numerically the accuracy of MRS estimations of the volume of different 3D targets aroundNahal Hever, shifting a 3D target inside the MRS loop and calculating the volume-estimation errors for each target position. The calculations covered targets of different sizes. The size and position of a target being unknown factors in a field s...
Geophysical Research Letters, 2006
Geochemistry, Geophysics, Geosystems, 2007
New high‐resolution airborne magnetic (HRAM) data along a 120‐km‐long section of the Dead Sea Tra... more New high‐resolution airborne magnetic (HRAM) data along a 120‐km‐long section of the Dead Sea Transform in southern Jordan and Israel shed light on the shallow structure of the fault zone and on the kinematics of the plate boundary. Despite infrequent seismic activity and only intermittent surface exposure, the fault is delineated clearly on a map of the first vertical derivative of the magnetic intensity, indicating that the source of the magnetic anomaly is shallow. The fault is manifested by a 10–20 nT negative anomaly in areas where the fault cuts through magnetic basement and by a <5 nT positive anomaly in other areas. Modeling suggests that the shallow fault is several hundred meters wide, in agreement with other geophysical and geological observations. A magnetic expression is observed only along the active trace of the fault and may reflect alteration of magnetic minerals due to fault zone processes or groundwater flow. The general lack of surface expression of the fault ...
Journal of Geophysical Research: Solid Earth, 2014
The northern Gulf of Elat/Aqaba is located in the transition between the deep marine basins of th... more The northern Gulf of Elat/Aqaba is located in the transition between the deep marine basins of the gulf and the shallow onland basins of the Arava Valley. Interpretation of 500 km of high‐resolution seismic reflection data collected across the northern shelf reveals the tectonic structure and evolution of this transition. Six NNE‐trending faults and one E‐W trending transverse fault are mapped. Slip rates are calculated based on measured offsets and age determination based on a radiocarbon‐calibrated sedimentation rate and a Quaternary age model. The most active fault is the Evrona Fault that absorbs most of the left lateral slip within the basin with an average sinistral slip rate of 0.7 ± 0.3 mm/yr through the Late Pleistocene and 2.3–3.4 mm/yr during the Holocene. Two intrabasin faults east of the Evrona Fault that have been inactive for the last several tens of thousands of years were mapped, and motion from these faults has likely transferred to the Evrona Fault. The basin is f...
Tectonophysics, 2020
Abstract The cities of Elat, Israel and neighboring Aqaba, Jordan are major economic, cultural, a... more Abstract The cities of Elat, Israel and neighboring Aqaba, Jordan are major economic, cultural, and seaport centers. They are located on the northern shore of the Gulf of Aqaba/Elat (GAE) directly on the Dead Sea Transform. Yet the precise location of the fault trace and its tectonic activity are lacking. The interpretation of seismic reflection profiles across the GAE beach and paleoseismic trench data located 2.2 km north of the shoreline provide evidence that the active offshore mapped Avrona Fault extends onland along the eastern side of the Elat Sabkha (mudflat), where three prominent fault strands crosscut the sedimentary fill. Mismatch of reflector geometry across the faults and flower structures indicate strike-slip faulting with a normal-slip component. Subsurface data from two trenching sites provide evidence for a minimum of two surface ruptures and two paleoliquefaction events. Faulting is constrained by radiocarbon dating for an Event 1 between 897 and 992 CE and Event 2 after 1294 CE. We suggest that the historically documented 1068 CE, and at least one later earthquake in 1458 or 1588 CE, ruptured the Elat Sabkha site. Based on fault mapping, we suggest a minimum value of M 6.6 for the 1068 CE earthquake. Whereas no surface rupture was observed for the 1212 CE historical earthquake, fluidized strata radiocarbon dated to before 1269–1389 CE identified as paleoliquefaction may be attributed to it. Two liquefaction sand-blows mapped in the trench likely formed after 1337 CE and before 1550 CE, which possibly occurred at the same time as in the second faulting event. Our data suggest that no large event occurred along the Avrona segment in the past ~430–550 years. Given a ~ 5 mm/yr slip rate, we conclude that a significant period of time passed since the last surface rupturing on the Avrona Fault, increasing its seismic potential.
Near Surface Geoscience 2012 – 18th European Meeting of Environmental and Engineering Geophysics, 2012
ABSTRACT Results of a geophysical study of the sinkhole development sites in the Dead Sea costal ... more ABSTRACT Results of a geophysical study of the sinkhole development sites in the Dead Sea costal area in Israel and Jordan are presented. Relations between sinkhole lineaments and faults have been studied using updated Seismic Reflection methodology. It was shown that sinkhole lineaments are arranged along the salt layer edge. We suggest that superficial coastal basins where salt formed were generated by sub-vertical displacements along faults. Such suggestion would agree two major competition models of sinkhole formation: structural model, considering control of faults and second one explaining sinkholes formation along salt edge. Such model suggests that salt layer edge is conformed to faults and sinkholes are arranged simultaneously along both salt edge and faults. This model will be verified shortly by analysis of boreholes and by other reflection sections carried out in past. Note, models presented in the paper enables us also to conclude that: (1) Salt edge can be considered as an ancient shoreline existing at the stage of salt unit formation (10,000 years ago). Modern sinkholes are formed along this ancient shoreline; and (2) Buried salt layer comes out far away of the modern Dead Sea shoreline permitting its investigation from surface.
Journal of Applied Geophysics
Since the 1990s a large number of sinkholes have appeared in the Dead Sea (DS) coastal area. Sink... more Since the 1990s a large number of sinkholes have appeared in the Dead Sea (DS) coastal area. Sinkhole development was triggered by the lowering of the DS level. In the literature the relationship between the sinkholes and the DS level is explained by intrusion of relatively fresh water into the aquifer thereby dramatically accelerating the salt dissolution with creation of subsurface caverns, which in turn cause sinkholes. The main goal of our project was detection and localization of relatively fresh groundwater. During our study we used the transient electromagnetic method (TEM) to measure the electrical resistivity of the subsurface. As a test site we selected Nahal Hever South which is typical for the DS coast. Our results show that resistivity of the shallow subsurface reflects its vertical and lateral structure, e.g., its main hydrogeological elements explain the inter-relations between geology, hydrogeology, and sinkholes. The TEM method has allowed detailed differentiation o...
ABSTRACT The microgravity method has been used for decades in oil and mineral exploration. Advanc... more ABSTRACT The microgravity method has been used for decades in oil and mineral exploration. Advances in microgravity equipment have improved the accuracy and efficiency of obtaining. Microgravity is a geophysical method that is increasingly being used for environmental and geotechnical investigations. Microgravity measurements respond to changes in subsurface density, and are a non-invasive way to effectively delineation of subsurface density variations. and identify the characterize subsurface voids and cavities. The integration of microgravity with other geophysical methods and geologic information will provide a more complete and accurate assessment of subsurface voids and cavities. A microgravity survey consists of making sensitive gravity measurements at discrete points on the ground surface. Spatial changes in gravity are referred to as gravity anomalies and are directly related to subsurface features with a measurable density contrast. Detection and delineation of subsurface cavities are the most common applications of Microgravimetry. Microgravimetry comes closest of all the geophysical methods to allowing a positive statement regarding the presence or absence of subsurface cavities at a site. Portable gravimeters are extremely sensitive instruments that measure relative differences in gravity from station to station. Gravimeters measure changes in the vertical component of gravity by balancing gravitational forces with a spring and mass system. Microgravimetry has shown itself as very sensitive tool in the western Dead Sea shore in Israel. Comprehensive anomaly of 80x50m in plane was detected from surface in the Nahal Hever south area. The great sinkhole formed at the place of the anomaly during some consequential years. The similar some less anomalies were discovered in the Ein Gedi site. From the Jordan side first Microgravity surveys were carried out in beginning of 2000th. Our studies were started in 2010 at the north of the Ghor Al-Haditha area where sinkhole development was delayed with respect to more southern areas. Microgravity study was carried out in parallel with the Micromagnetic and other surface methods (ERT, GPR etc) that allows combined interpretation of results. Some anomalies of the microgravity and Micromagnetic fields have been detected, which would be evidences of possible future collapses. Acknowledgements This publication was made possible through support provided by the U.S. Agency for International Development (USAID) and MERC Program under terms of Award No M27-050.
Near Surface 2007 - 13th EAGE European Meeting of Environmental and Engineering Geophysics, 2007
Results of investigations carried out by the Geological Survey of Israel and the Geophysical Inst... more Results of investigations carried out by the Geological Survey of Israel and the Geophysical Institute of Israel reveal that the development of sinkholes in the Dead Sea coast is linked to subsurface salt formations and change of fresh – saline water interface caused by the drop of the Dead Sea level. Since groundwater is seen as the major reason for sinkhole development, it was decided to apply the Magnetic Resonance Sounding (MRS) method to investigate aquifers in potentially dangerous areas. In 2005 and 2007, two MRS surveys supported by NATO project SfP N° 981128 were performed in the area. Our results reveal a very heterogeneous aquifer with two orders of the transmissivity variation around the investigated area. It was observed with MRS that when sinkhole hazard takes place it causes 5-10 folds drop of the transmissivity. Formation of new caverns was not observed. Numerical modeling reveals that under Nahal Hever conditions the water table can be measured with MRS with the uncertainty of a few meters. However, accuracy of MRS is sufficient for monitoring of the transmissivity of aquifers in sinkhole hazardous areas where ground collapse may modify significantly the subsurface.
Tectonophysics, 2002
Gravity and magnetic data were collected and used to study the crustal structure of Jordan. Three... more Gravity and magnetic data were collected and used to study the crustal structure of Jordan. Three new geophysical maps of Jordan were created: a Moho discontinuity map, a crystalline basement surface map, and a map showing the lowest limit of magnetic blocks. Depths of the Curie Isotherm were also calculated. Results indicate that the depth to the Moho discontinuity in Jordan varies from 32 to 33 km in the northwest to 38 km in the southeast. The basement complex rocks outcrop on the surface in the southwest but lie at about 8 km in the northeast. The Curie Isotherm (585 jC) lies at a depth of about 10 km in the area east of the Dead Sea and dips southeastward towards the Al-Sirhan (Wadi Sirhan), southeast Jordan, where it is located at 35 km depth. Local isostasy of rock masses (blocks) in Jordan does not occur. Nevertheless, this does not rule out the possible existence of isostasy in a regional scale at greater depths within the mantle.
Near Surface 2011 - 17th EAGE European Meeting of Environmental and Engineering Geophysics, 2011
ABSTRACT A new geophysical methodology for sinkhole hazard assessment is under development. The k... more ABSTRACT A new geophysical methodology for sinkhole hazard assessment is under development. The key point of the new methodology is delineating salt distribution, in particular the salt edge, based on the time electromagnetic method analysis. We consider a new approach to use the Transient Electromagnetic (TEM) method in its FAST modification for studying the distribution of bulk resistivity in the vicinity of the salt edge and salt layer properties: porosity, depth and thickness. This methodology is based on separate resistivity mapping of the subsurface east and west of salt layer edge that was revealed by seismic refraction method. Then we can separate the investigation area into two“sub-areas”: (1) “salt” area, where the measured resistivity is influenced by the salt porosity (estimated from the Archie’s law); (2) “no-salt” area, where the measured resistivity is influenced by the groundwater salinity estimated using the resistivity-salinity inter-relations obtained for the Dead Sea region. West of the salt edge resistivity of aquifer associated with the aquifer salinity is mapped, whereas east of that salt layer resistivity related to its porosity is mapped. In Jordan it works reversely.
International Journal of Geophysics, 2013
Microgravity investigations are now recognized as a powerful tool for subsurface imaging and espe... more Microgravity investigations are now recognized as a powerful tool for subsurface imaging and especially for the localization of underground karsts. However numerous natural (geological), technical, and environmental factors interfere with microgravity survey processing and interpretation. One of natural factors that causes the most disturbance in complex geological environments is the influence of regional trends. In the Dead Sea coastal areas the influence of regional trends can exceed residual gravity effects by some tenfold. Many widely applied methods are unable to remove regional trends with sufficient accuracy. We tested number of transformation methods (including computing gravity field derivatives, self-adjusting and adaptive filtering, Fourier series, wavelet, and other procedures) on a 3D model (complicated by randomly distributed noise), and field investigations were carried out in Ghor Al-Haditha (the eastern side of the Dead Sea in Jordan). We show that the most effecti...
Environmental Earth Sciences, 2021
The presence of buried salt layer in the Ghor Al-Haditha area is discussed concerning sinkhole ha... more The presence of buried salt layer in the Ghor Al-Haditha area is discussed concerning sinkhole hazard. Numerous geophysical methods such as seismic refraction (SRFR), reflection (SRFL), seismic tomography, multichannel analysis of surface waves (MASW) were developed earlier for the salt layer identification. Geophysical criteria of salt parameters (such as longitudinal Vp and shear Vs wave velocities) were established to identify salt layers. This paper presents new geophysical results proving the salt extension in the Dead Sea (DS) coastal area in its eastern shore potentially representing a sinkhole hazard. The reprocessing technique of MASW data using the synthetic modeling enabled us to detect salt layer characteristics such as depth to its top, the thickness of the layer, and its Vs velocity. It was established that a salt layer with 7–10 m thick is located at a depth of 37–41 m and is characterized by shear-wave velocity (Vs) of 850–1200 m/s. Similar results were obtained by the Transient Electromagnetic (TEM) resistivity method, which detected a comparatively resistive salt layer at a background of very low resistivity. The resolution of the TEM method allows detecting a salt layer of 3 m thick and more at a depth of 39–40 m. Seismic refraction data processing has shown the presence of a salt layer with a velocity of more than 2900 m/s at approximately or the same depths. Analysis of seismic tomography data also confirms the parameters of the discovered target. Analysis of results of geophysical studies in the western and eastern DS shores, comparison of geological conditions in shores, and sinkhole development, enabled us to conclude with a high probability that salt layers exist in both shores and sinkhole development is determined here by similar mechanisms.
Near Surface 2005 - 11th European Meeting of Environmental and Engineering Geophysics, 2005
P078 SINKHOLE HAZARD ASSESMENT IN THE DEAD SEA AREA – TWO GEOPHYSICAL ASPECTS OF THE PROBLEM 1 Su... more P078 SINKHOLE HAZARD ASSESMENT IN THE DEAD SEA AREA – TWO GEOPHYSICAL ASPECTS OF THE PROBLEM 1 Summary A combination of different surface geophysical techniques is used as a tool for sinkhole development prediction. While each of the geophysical methods alone does not in general facilitate reliable detection of subsurface voids the combination of different geophysical methods does allow us to detect (1) the dissolution caves within the salt unit (Microgravity and Seismic Diffraction); (2) the depth to the water table (MRS) and (3) distribution of the bulk resistivity (related to salinity) over the space (TEM and CVES) with greater
ABSTRACT We consider a new approach to use the geoelectric methods for studying the both uppermos... more ABSTRACT We consider a new approach to use the geoelectric methods for studying the both uppermost part of section and salt layer conditions in the sinkhole development sites. The Electric Resistivity Tomography (ERT) is used here to detect shallow deformations in subsurface sediments. Resistivity prospecting yields information about both lateral and vertical distribution of resistivity through the geological section and can therefore be used in both qualitative and quantitative ways for the identification of structure and features at shallow depths. As it follows from the modified Archie's Law, resistivity of the unsaturated sediments is determined by their porosity. The higher the porosity, the higher is the resistivity. It will also depend on volume of the electrolyte in pores and resistivity of the fluid . Note that after mechanical models available the higher porosity in sinkhole development sites is caused by the void presence at depth. 2D and 3D mapping was carried out in the Mineral Beach area in Israel and in the Ghor Al-Haditha site in Jordan. ERT method shown high resistivity anomaly of some thousands Ohm-m located along the salt edge. The Transient Electromagnetic Method (TEM) also referred to as the Time Domain Electromagnetic Method (TDEM) is sensitive to the bulk resistivity (conductivity) of the studied medium, especially in the low-resistivity range. Transient Electromagnetic (TEM) method in its FAST modification was used for studying the salt layer conditions (salt porosity, depth of the salt top and thickness of the salt layer) and distribution of bulk resistivity in vicinity of the salt border (to resolve the problem of water salinity). The methodology includes numerous measurements through the sinkhole development areas. Earlier the TEM method was used extensively worldwide for locating the fresh-saline water interface in coastal areas and for estimating groundwater salinity. In our study we have mapped salt layer geometrical parameters (e.g. depth to salt top, salt layer thickness) as well as salt resistivity that is measure of salt porosity. New methodology permits also 2D and 3D presentation of the acquired results in spite methodology itself of the data acquisition is of 1D in its origin. Acknowledgements This study has been supported by the USAID MERC Program M27-050
Journal of Environmental and Engineering Geophysics, 2000
A DC resistivity profiling experiment was conducted over a buried cavity using a SYSCAL-R2 resist... more A DC resistivity profiling experiment was conducted over a buried cavity using a SYSCAL-R2 resistivity instrument at the location of a proposed highway at the Ras en Naqab escarpment, Aqaba Province, southwest Jordan. The objective of the study was to evaluate the resolution of the resistivity technique in detecting and locating significant anomalies (high resistivity) over underground cavities. Resistivity profiling measurements were carried out utilizing the following arrays: (1) Alpha-Wenner; (2) Beta-Wenner; (3) Gamma-Wenner; (4) Pole-Pole; (5) Combined Head-on. Results of the survey demonstrated a strong correlation between resistivity anomalies and a subsurface void. An open and air-filled cavity exhibits markedly high-resistivity anomalies. In addition, the survey indicated that caverns with diameters as small as [Formula: see text] can be detected at shallow depths below surface and can be positioned using the resistivity profiling method. Correlations between field results ...
GEOPHYSICS, 2008
Magnetic resonance sounding (MRS) is a geophysical technique developed for groundwater exploratio... more Magnetic resonance sounding (MRS) is a geophysical technique developed for groundwater exploration. This technique can be used for investigating karst aquifers. Generally, the study of a karst requires a 3D field setup and corresponding multichannel data-acquisition instruments. Now only single-channel MRS equipment is available; i.e., the time needed for a 3D MRS field survey is multiplied by a factor of four or five. Where karst caverns are natural hazards, as in the Dead Sea coastal area at Nahal Hever, Israel, even an approximate localization of potentially dangerous zones and a corresponding estimation of the hazard dimensions are useful. We studied numerically the accuracy of MRS estimations of the volume of different 3D targets aroundNahal Hever, shifting a 3D target inside the MRS loop and calculating the volume-estimation errors for each target position. The calculations covered targets of different sizes. The size and position of a target being unknown factors in a field s...
Geophysical Research Letters, 2006
Geochemistry, Geophysics, Geosystems, 2007
New high‐resolution airborne magnetic (HRAM) data along a 120‐km‐long section of the Dead Sea Tra... more New high‐resolution airborne magnetic (HRAM) data along a 120‐km‐long section of the Dead Sea Transform in southern Jordan and Israel shed light on the shallow structure of the fault zone and on the kinematics of the plate boundary. Despite infrequent seismic activity and only intermittent surface exposure, the fault is delineated clearly on a map of the first vertical derivative of the magnetic intensity, indicating that the source of the magnetic anomaly is shallow. The fault is manifested by a 10–20 nT negative anomaly in areas where the fault cuts through magnetic basement and by a <5 nT positive anomaly in other areas. Modeling suggests that the shallow fault is several hundred meters wide, in agreement with other geophysical and geological observations. A magnetic expression is observed only along the active trace of the fault and may reflect alteration of magnetic minerals due to fault zone processes or groundwater flow. The general lack of surface expression of the fault ...
Journal of Geophysical Research: Solid Earth, 2014
The northern Gulf of Elat/Aqaba is located in the transition between the deep marine basins of th... more The northern Gulf of Elat/Aqaba is located in the transition between the deep marine basins of the gulf and the shallow onland basins of the Arava Valley. Interpretation of 500 km of high‐resolution seismic reflection data collected across the northern shelf reveals the tectonic structure and evolution of this transition. Six NNE‐trending faults and one E‐W trending transverse fault are mapped. Slip rates are calculated based on measured offsets and age determination based on a radiocarbon‐calibrated sedimentation rate and a Quaternary age model. The most active fault is the Evrona Fault that absorbs most of the left lateral slip within the basin with an average sinistral slip rate of 0.7 ± 0.3 mm/yr through the Late Pleistocene and 2.3–3.4 mm/yr during the Holocene. Two intrabasin faults east of the Evrona Fault that have been inactive for the last several tens of thousands of years were mapped, and motion from these faults has likely transferred to the Evrona Fault. The basin is f...
Tectonophysics, 2020
Abstract The cities of Elat, Israel and neighboring Aqaba, Jordan are major economic, cultural, a... more Abstract The cities of Elat, Israel and neighboring Aqaba, Jordan are major economic, cultural, and seaport centers. They are located on the northern shore of the Gulf of Aqaba/Elat (GAE) directly on the Dead Sea Transform. Yet the precise location of the fault trace and its tectonic activity are lacking. The interpretation of seismic reflection profiles across the GAE beach and paleoseismic trench data located 2.2 km north of the shoreline provide evidence that the active offshore mapped Avrona Fault extends onland along the eastern side of the Elat Sabkha (mudflat), where three prominent fault strands crosscut the sedimentary fill. Mismatch of reflector geometry across the faults and flower structures indicate strike-slip faulting with a normal-slip component. Subsurface data from two trenching sites provide evidence for a minimum of two surface ruptures and two paleoliquefaction events. Faulting is constrained by radiocarbon dating for an Event 1 between 897 and 992 CE and Event 2 after 1294 CE. We suggest that the historically documented 1068 CE, and at least one later earthquake in 1458 or 1588 CE, ruptured the Elat Sabkha site. Based on fault mapping, we suggest a minimum value of M 6.6 for the 1068 CE earthquake. Whereas no surface rupture was observed for the 1212 CE historical earthquake, fluidized strata radiocarbon dated to before 1269–1389 CE identified as paleoliquefaction may be attributed to it. Two liquefaction sand-blows mapped in the trench likely formed after 1337 CE and before 1550 CE, which possibly occurred at the same time as in the second faulting event. Our data suggest that no large event occurred along the Avrona segment in the past ~430–550 years. Given a ~ 5 mm/yr slip rate, we conclude that a significant period of time passed since the last surface rupturing on the Avrona Fault, increasing its seismic potential.
Near Surface Geoscience 2012 – 18th European Meeting of Environmental and Engineering Geophysics, 2012
ABSTRACT Results of a geophysical study of the sinkhole development sites in the Dead Sea costal ... more ABSTRACT Results of a geophysical study of the sinkhole development sites in the Dead Sea costal area in Israel and Jordan are presented. Relations between sinkhole lineaments and faults have been studied using updated Seismic Reflection methodology. It was shown that sinkhole lineaments are arranged along the salt layer edge. We suggest that superficial coastal basins where salt formed were generated by sub-vertical displacements along faults. Such suggestion would agree two major competition models of sinkhole formation: structural model, considering control of faults and second one explaining sinkholes formation along salt edge. Such model suggests that salt layer edge is conformed to faults and sinkholes are arranged simultaneously along both salt edge and faults. This model will be verified shortly by analysis of boreholes and by other reflection sections carried out in past. Note, models presented in the paper enables us also to conclude that: (1) Salt edge can be considered as an ancient shoreline existing at the stage of salt unit formation (10,000 years ago). Modern sinkholes are formed along this ancient shoreline; and (2) Buried salt layer comes out far away of the modern Dead Sea shoreline permitting its investigation from surface.
Journal of Applied Geophysics
Since the 1990s a large number of sinkholes have appeared in the Dead Sea (DS) coastal area. Sink... more Since the 1990s a large number of sinkholes have appeared in the Dead Sea (DS) coastal area. Sinkhole development was triggered by the lowering of the DS level. In the literature the relationship between the sinkholes and the DS level is explained by intrusion of relatively fresh water into the aquifer thereby dramatically accelerating the salt dissolution with creation of subsurface caverns, which in turn cause sinkholes. The main goal of our project was detection and localization of relatively fresh groundwater. During our study we used the transient electromagnetic method (TEM) to measure the electrical resistivity of the subsurface. As a test site we selected Nahal Hever South which is typical for the DS coast. Our results show that resistivity of the shallow subsurface reflects its vertical and lateral structure, e.g., its main hydrogeological elements explain the inter-relations between geology, hydrogeology, and sinkholes. The TEM method has allowed detailed differentiation o...
ABSTRACT The microgravity method has been used for decades in oil and mineral exploration. Advanc... more ABSTRACT The microgravity method has been used for decades in oil and mineral exploration. Advances in microgravity equipment have improved the accuracy and efficiency of obtaining. Microgravity is a geophysical method that is increasingly being used for environmental and geotechnical investigations. Microgravity measurements respond to changes in subsurface density, and are a non-invasive way to effectively delineation of subsurface density variations. and identify the characterize subsurface voids and cavities. The integration of microgravity with other geophysical methods and geologic information will provide a more complete and accurate assessment of subsurface voids and cavities. A microgravity survey consists of making sensitive gravity measurements at discrete points on the ground surface. Spatial changes in gravity are referred to as gravity anomalies and are directly related to subsurface features with a measurable density contrast. Detection and delineation of subsurface cavities are the most common applications of Microgravimetry. Microgravimetry comes closest of all the geophysical methods to allowing a positive statement regarding the presence or absence of subsurface cavities at a site. Portable gravimeters are extremely sensitive instruments that measure relative differences in gravity from station to station. Gravimeters measure changes in the vertical component of gravity by balancing gravitational forces with a spring and mass system. Microgravimetry has shown itself as very sensitive tool in the western Dead Sea shore in Israel. Comprehensive anomaly of 80x50m in plane was detected from surface in the Nahal Hever south area. The great sinkhole formed at the place of the anomaly during some consequential years. The similar some less anomalies were discovered in the Ein Gedi site. From the Jordan side first Microgravity surveys were carried out in beginning of 2000th. Our studies were started in 2010 at the north of the Ghor Al-Haditha area where sinkhole development was delayed with respect to more southern areas. Microgravity study was carried out in parallel with the Micromagnetic and other surface methods (ERT, GPR etc) that allows combined interpretation of results. Some anomalies of the microgravity and Micromagnetic fields have been detected, which would be evidences of possible future collapses. Acknowledgements This publication was made possible through support provided by the U.S. Agency for International Development (USAID) and MERC Program under terms of Award No M27-050.
Near Surface 2007 - 13th EAGE European Meeting of Environmental and Engineering Geophysics, 2007
Results of investigations carried out by the Geological Survey of Israel and the Geophysical Inst... more Results of investigations carried out by the Geological Survey of Israel and the Geophysical Institute of Israel reveal that the development of sinkholes in the Dead Sea coast is linked to subsurface salt formations and change of fresh – saline water interface caused by the drop of the Dead Sea level. Since groundwater is seen as the major reason for sinkhole development, it was decided to apply the Magnetic Resonance Sounding (MRS) method to investigate aquifers in potentially dangerous areas. In 2005 and 2007, two MRS surveys supported by NATO project SfP N° 981128 were performed in the area. Our results reveal a very heterogeneous aquifer with two orders of the transmissivity variation around the investigated area. It was observed with MRS that when sinkhole hazard takes place it causes 5-10 folds drop of the transmissivity. Formation of new caverns was not observed. Numerical modeling reveals that under Nahal Hever conditions the water table can be measured with MRS with the uncertainty of a few meters. However, accuracy of MRS is sufficient for monitoring of the transmissivity of aquifers in sinkhole hazardous areas where ground collapse may modify significantly the subsurface.
Tectonophysics, 2002
Gravity and magnetic data were collected and used to study the crustal structure of Jordan. Three... more Gravity and magnetic data were collected and used to study the crustal structure of Jordan. Three new geophysical maps of Jordan were created: a Moho discontinuity map, a crystalline basement surface map, and a map showing the lowest limit of magnetic blocks. Depths of the Curie Isotherm were also calculated. Results indicate that the depth to the Moho discontinuity in Jordan varies from 32 to 33 km in the northwest to 38 km in the southeast. The basement complex rocks outcrop on the surface in the southwest but lie at about 8 km in the northeast. The Curie Isotherm (585 jC) lies at a depth of about 10 km in the area east of the Dead Sea and dips southeastward towards the Al-Sirhan (Wadi Sirhan), southeast Jordan, where it is located at 35 km depth. Local isostasy of rock masses (blocks) in Jordan does not occur. Nevertheless, this does not rule out the possible existence of isostasy in a regional scale at greater depths within the mantle.
Near Surface 2011 - 17th EAGE European Meeting of Environmental and Engineering Geophysics, 2011
ABSTRACT A new geophysical methodology for sinkhole hazard assessment is under development. The k... more ABSTRACT A new geophysical methodology for sinkhole hazard assessment is under development. The key point of the new methodology is delineating salt distribution, in particular the salt edge, based on the time electromagnetic method analysis. We consider a new approach to use the Transient Electromagnetic (TEM) method in its FAST modification for studying the distribution of bulk resistivity in the vicinity of the salt edge and salt layer properties: porosity, depth and thickness. This methodology is based on separate resistivity mapping of the subsurface east and west of salt layer edge that was revealed by seismic refraction method. Then we can separate the investigation area into two“sub-areas”: (1) “salt” area, where the measured resistivity is influenced by the salt porosity (estimated from the Archie’s law); (2) “no-salt” area, where the measured resistivity is influenced by the groundwater salinity estimated using the resistivity-salinity inter-relations obtained for the Dead Sea region. West of the salt edge resistivity of aquifer associated with the aquifer salinity is mapped, whereas east of that salt layer resistivity related to its porosity is mapped. In Jordan it works reversely.
International Journal of Geophysics, 2013
Microgravity investigations are now recognized as a powerful tool for subsurface imaging and espe... more Microgravity investigations are now recognized as a powerful tool for subsurface imaging and especially for the localization of underground karsts. However numerous natural (geological), technical, and environmental factors interfere with microgravity survey processing and interpretation. One of natural factors that causes the most disturbance in complex geological environments is the influence of regional trends. In the Dead Sea coastal areas the influence of regional trends can exceed residual gravity effects by some tenfold. Many widely applied methods are unable to remove regional trends with sufficient accuracy. We tested number of transformation methods (including computing gravity field derivatives, self-adjusting and adaptive filtering, Fourier series, wavelet, and other procedures) on a 3D model (complicated by randomly distributed noise), and field investigations were carried out in Ghor Al-Haditha (the eastern side of the Dead Sea in Jordan). We show that the most effecti...