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Second EAGE International Conference on Engineering Geophysics
- Conference date: 24 Nov 2013 - 27 Nov 2013
- Location: Al Ain, United Arab Emirates
- ISBN: 978-90-73834-66-8
- Published: 24 November 2013
1 - 50 of 71 results
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Simulation of Time-lapse Geophysical Datasets in Cavity Remediation Applications
Authors A.D. Booth, H. El-Kaliouby, A. Swidinsky and P. StylesThe near-surface geology of many regions of the Arabian Peninsula is dominated by karstic carbonate and, consequently, construction projects in the Peninsula can be adversely affected by cavities and sinkholes. The risk posed by potential cavity collapse is often mitigated by grouting, although their initial detection and characterisation is facilitated by geophysical survey. Typically, resistivity, microgravity and surface-wave seismic methods are applied to cavity detection. In this paper, we extend the use of these geophysical methods to time-lapse applications, in which the remediation of the cavity is monitored during and after the grouting operation. Furthermore, we explore the potential for ground penetrating radar (GPR) methods to complement the established suite of cavity-detection methods. These are potentially powerful in time-lapse applications since data acquisition rates are very high. We simulate GPR and resistivity acquisitions over a simple cavity geometry, which comprises two interconnected rectangular sections, and investigate the potential to a) image the fine-scale detail of the cavity, and b) monitor the progress of the grouting operation. GPR models consider common offset antennas, of 250 MHz centre-frequency; resistivity models comprise 96 electrodes installed at 0.3 m intervals, used in a Wenner array configuration. Resistivity data lack the vertical and spatial resolution to monitor the remediation during grouting, but do provide useful before-and-after snapshots of the cavity. By contrast, the GPR wavelet is easily able to resolve the shrinking air-gap inside the cavity as the grout is injected. We hope to extend these synthetic analyses to a real-data application, and consider the use of multiple data sources in a constrained inversion strategy.
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Results from a 10-year AEM Mapping Programme of Buried Tunnel Valleys in Denmark
Authors F. Jorgensen and P. SandersenExtensive mapping with airborne EM has since 2003 revealed intricate patterns of buried tunnel valleys in the Danish subsurface. Several generations of cross-cutting valleys are found making up a highly complicated geological setting. The valleys play a vital role for the Danish water supply because they are assumed to host about 50 % of all extractable groundwater, but they are also important because they impose a significant impact on groundwater flow. Especially three properties of the valleys are essential to map: 1) their spatial extent, 2) their internal architecture, and 3) the lithology of the infill and surrounding environment. Borehole data constitute an insufficient basis for 1) and 2). Instead, techniques like the airborne SkyTEM system providing 3D data are required. Almost 20.000 km2 have been mapped with the TEM method resulting in more than 5000 km mapped buried valleys. With the SkyTEM system full information about the spatial extent of the valleys (1) can normally be achieved, but also information about the internal architecture (2) and lithology (3) is obtained to some extent. Collection of seismic data and borehole data provide supplementary information about (2) and (3) at selected sites.
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Geotechnics Shallow and Detailed: Is AEM Up for the Challenge?
Authors A. Menghini, A. Viezzoli, C. Del Ventisette, A. Manzella, D. Montanari, N. Giannelli and S. MorettiApplied Geophysics to Engineering, Geotechnics and Environment is generally synonymous of shallow target, but, at the same time, it demands a detailed reconstruction of the subsurface. The question is:”Is the Airborne EM ready to accept this challenge ?”. Our answer is positive, based on experiences of some case studies, dealing with landslides, shallow geological investigation and so on. Indeed the applications of AEM to geotechnical issues are very few: Beard and Lutro [1] showed the case of an airborne prospect, by using not only EM, but also magnetic, radiometric and VLF data, for the planning of a railroad in Norway; Pfaffhuber et al. [2] used the AEM for the study of rock slides and tunnelling hazards in Norway again; several are the application of the method for environmental purposes, such as potential hazards at coal-waste impoundments [3] or waste site characterization [4, 5, 6, 7]. Other rare applications are focused on the supply of sands and gravels for engineering purposes [8], while the detection of lithologic distributions in alluvial aquifer, due to hydrogeological purposes, is more frequent [9, 10,11].
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2D Seismic Reflection Survey for Mapping of Bedrock and Geological Structures in the Vicinity of Jeddah-Airport
Authors F. Bahloul, D. Orlowsky and A. Abdel Rahman Abdel RaoufFor the development of the King Abdulaziz International Airport (KAIA), Jeddah; Saudi Arabia 2D seismic reflection survey has been performed to provide information for the groundwater assessment study. The evolution of the geological and hydro-geological condition is a preliminary task to be conducted for designing the foundation and for studying its impact on the environment. The objective of the 2D seismic reflection survey was detection and mapping of the bedrock layer up to 500 m depth, defining the aquifer hydro-geological features and estimation and delineation of the major geological structures (faults, shear zones, joints). The processed seismic cross-sections revealed many structures and faults and defined different hydrological units (bedrock depth, weathered bedrock, alluvium deposits and evaporite as well as clay layer and lenses). The results of the 2D seismic survey will be presented. The visualisation in 2D and 3D plots of the geological units and structures are provided to give an impression about their spatial extension and distribution.
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Site Investigation Using 2D Resistivity Imaging to Detect Subsurface Cavities and Weak Zones at Mosul’s Stadium, North Iraq (A Case Study)
More LessKarst voids were encountered during a stadium construction in Mosul city, NE Iraq. Drilling in the site showed the presence of cavities and zone of weak rocks in some boreholes. However, the boreholes show only a limited picture of the subsurface beneath the borehole only, while drilling in all the site is expensive and time consuming. Surface geophysical methods can successfully be applied to detecting and mapping cavities, fractures and other karst features. These methods provide in-situ measurements of the subsurface non-invasively and can therefore provide a dramatic increase in spatial and temporal coverage. A 2D resistivity imaging has been one of the most effective methods in this regard in that it often can provide a detailed picture of underground conditions without digging, and it lacks many of the limitations of other geophysical tools. The method was successfully applied in the proposed site of the Mosul Stadium Project, which gave very clear pictures of the cavities and weak rock zones in the subsurface.
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Gravity Analysis for Geothermal Reconnaissance in Costa Rica
Authors Hakim SAIBI and E. AboudTwo geothermal fields in Costa Rica were investigated by gravity surveys in an attempt to delineate their subsurface structures. The surveys improve the understanding of the relation between the geothermal systems and subsurface structure. The gravity data are analyzed using integrated gradient interpretation techniques such as the Horizontal Gradient (HG) and Euler Deconvolution methods. With these techniques, many faults are detected and compared with those found in the surface geology. The results of this study lead to a better understanding of the geothermal system in the study area and may aid in future geothermal exploration.
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Surface to Borehole Radial Electrical Resistivity Measurement Using L-Shape Array
Authors H. Baker and K. BenhamamThe different resistivity techniques are being extensively used in environmental and civil engineering to investigate the subsurface conditions. However, the application of the known ground resistivity techniques is subjected to the space availability in the investigated areas. Therefore, in order to avoid the space restriction, geophysicists use the borehole tomography in two or more wells. This approach requires more time and adds cost to survey execution. In this work, the use of the L-Shape resistivity array is being proposed as borehole to surface resistivity measurement technique. The procedure is to put the potential electrodes in the well and to keep the current electrodes on the surface and to conducted the measurements with different spacing in a radial manner around the borehole.
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Monitoring Rock and Foundation Stability by Observing the Electromagnetic Fields, City of 15th of May, Cairo, Egypt
Authors M.A. Atya, O.H. Hachay, O.Y. Hachay and A.A. RagabThe present work provides a technical procedure to estimate the geomechanical and geoelectrical parameters as key information of the dynamic state and stability of the massive structure. It involves the application of Control Source Electromagnetic "CSEM" approach developed by GIF UB RAS to image the ranked deformation levels in the massive structure. The Wide Profile System of Observation had been used to monitor the three component electromagnetic field along predefined measuring lines at Quarter 27 in the City of 15th of May, Helwan, Egypt. Four cycles of observation had been carried out in 2008, 2010, 2011, and 2012. The acquired data set had been subjected to analytical processing procedure to estimate the changes in the geotechnical parameters over time of observation. Interpreting the measured data concluded that the general dynamic state at the area is getting worse over the time, this is reflected in the crack's intensities and positions, also on the changes in the lateral distribution of the geoelectrical heterogeneity as indicator for water saturation.
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Application of Geophysical Surveys to Geotechnical Investigations
Authors T. Meglich and N. BouzidThe case studies presented here illustrate the usefulness of geophysical surveys to aid more expensive conventional drilling programs. In all case studies, the use of a mobile, high-speed time-domain electromagnetic system is demonstrated. The geophysical data was acquired at several project locations in the United States and the United Arab Emirates.
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Geophysical Investigations Holy Mosque Expansion Site
More Lesshe Holy Mosque, located on Mecca, Saudi Arabia is the most important place on Earth. Geophysical investigations GPR and Downhole Seismic Velocity were carried out on the Haram Expansion Site to achieve the objectives within the limits of the geophysical possibilities and to obtain accurate information about the subsurface geology in order to prepare strong solid foundation to the structural civil engineers and architects of the proposed expansion area for the Holy site.
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3D Electrical Resistivity Imaging as a Tool for Quantification of Landfills' Leachate
Authors A. Abdulrahman, M.N.M. Nawawi and R. SaadAn alternative to Water Balance Method (WBM) for estimating the quantity of leachate at landfill sites is presented in this paper. The WBM emphasis is on generating rate, while this geophysical approach estimates the in-situ quantity of leachate. The 3D inverted sections were generated using RES2DINV and RES3DINV programs. The resistivity variation in the inverted pseudo-sections clearly delineated the contaminant leachate plume (ρ < 5 Ωm), which facilitated its volume computation. The effective porosity values of clay (0.15) and sand/gravel (0.28) deduced from lithology logs were used in calculating the imaged sections of the leachate. Electrical conductivity values of 1782 µS/cm and 4521 µS/cm were determined for uncontaminated and contaminated zones respectively. A total leachate volume of 2.21 x 102 m3 was estimated beneath the 1600 m2 surveyed area.
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The Use of GPR to Locate Buried Septic Tanks – Al Ain City, UAE
Authors M. AlNnuaimi and H. BenhamamGeophysical survey has been conducted by using the Ground Penetrating Radar to locate and delimit a number of old septic tanks in the city of Al-Ain, UAE; and avoid any unnecessary excavations and possible environmental problems. The exact locations and dimensions of these very old tanks are not known due to lack of construction plans or maps. The GPR survey gave excellent results by obtaining not only the exact locations but also the dimensions, the depths and heights of these tanks
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Looking for Tawam Through the Sand: Geophysical Investigations at Oud Al Toba, Al-Ain, UAE
Authors W. Al Tikriti, W.A. Omar, D.A. Al Tawalbeh, A.R. Al Nuaimi and A.K. Al KaabiSince they have been developed in the last few decades geophysical techniques have rarely been applied on archaeology in the United Arab Emirates. This article presents a Ground Penetrating Radar (GPR) survey of an Early Islamic site in Al Ain (8-10th centuries AD), which has been tentatively identified as ancient ‘Tawam’, the old name of Al Ain. The previous archaeological investigations at the site (1999-2000), without applying geophysical surveys at the site, will be briefed whilst the results of the GPR surveys (2011-2013) and sub-sequent test-excavations are provided. Ariel photos of 1968 shows the area of the site covered with sand dunes which seems to have been bulldozed and leveled off shortly afterwards.
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In Search of the Pyramid of a Missing Pharaoh at South-Saqqara (Egypt)
Authors R. Guerin, V. Dobrev, C. Camerlynck and F. RejibaGeophysical surveys at South-Saqqara (Egypt) allow to detect a funerary temple of a pyramid of the missing Pharaoh Userkare.
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Ground Penetrating Radar Surveys to Detect Ancient Aflaj in the Hajar Region of Oman
Authors A.D. Booth, J.C. Orchard, J.J. Orchard and A.D.H. BartlettGround penetrating radar (GPR) is a standard tool in archaeological surveying, and offers high-resolution imaging of buried archaeological targets. In this paper, we explore the potential of GPR methods to detect ancient irrigation channels, aflaj (singular: falaj), in Oman’s Hajar Region. These aflaj, dating from the second-half of the 4th millennium BC, are associated with ancient settlements called Hajar Oasis Towns, and provide the most reliable means of water supply in the region. Locating the aflaj with geophysical methods can be difficult since they typically lack a geophysical contrast with their host material. They occasionally have anomalous magnetic properties, allowing them to be detected with magnetometry and thereafter excavated. However, where a magnetic contrast is absent, we trial the application of GPR. During two field seasons, we acquired GPR data (using a 500 MHz Sensors&Software system) around three Hajar Oasis Towns close to the modern towns of Bahla and Bisya, in Oman. For the most part, we acquired pseudo-3D GPR grids sampled at 5x50 cm resolution. As with magnetomtery, it appears that aflaj are only occasionally detectable with GPR. In one survey grid, a falaj is detectable and is shown to extend further north from the current limit of its excavation; however, no aflaj are confirmed elsewhere, and they cannot be detected even when acquired over known falaj positions. Nonetheless, our surveys have revealed new archaeological features of the Hajar Oasis Towns, including buried pits from which ancient pottery fragments were recovered. We suggest that the material filling the ancient aflaj generally lacks sufficient physical contrast with either its overburden or host-rock to be reliably imaged with GPR, but that GPR has other interesting applications in the Hajar Region.
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A Multi-Methodological Approach for Archaeology
Authors G. Morelli, G. Pagano, S. Floris, M. Pelorosso, M. Di Nezza, G.A. Pichardo, F. Cecchini, S. Margottini and M. Di FilippoArcheologycal and geophysical sciences proceeded parallely for years, reaching different goals but following common task to improve the knowledge of the subsurface. Today these sciences are approaching very close, even because of the successes that geophysics is getting with the help of electronics and informatics for archaeological discoveries. Modern technologies allow to obtain defined and clear subsoil images, spending quite short time to recognize where focusing the attention of excavations. In order to obtain the best results, archaeological studies before excavation must includes: an accurate historical and bibliographical research, and a comparison of the data obtained with different geophysical surveys carried out in the same area considered interesting from the archaeological point of view. Comparison of different geophysical methods, allows to have confirmation of what every single method points out, therefore, the synergy between the two figures, the archaeologist and the geophysical, can surely create a winning combination.
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Induced Seismicity and its Relationship to Shale Gas Hydrofracturing
More LessShale Gas exploration in the UK began in 2010 with five stages of hydraulic fracturing of the Bowland Shale. Hydofracturing in Cuadrilla Preese Hall-1 used 5 couplets of mini- and main-fracs with c. 10,000 bbl per stage, hydraulically isolated from each other during injection. An earthquake of 2.3 ML, a 1.5ML and a series of smaller events occurred from 31st March through May 2011 when work ceased for detailed analysis. Seismicity commenced after stages 2, 4 and 5; the largest occurring 10 hours after stage-2 shut-in. Seismological analysis using observations from seismometers emplaced after the 2.3 event, and regional data detected 55 seismic events from ML-2 to ML2, with 14 between ML 0.2 to M2.3, indicating a low B-value of 0.8 (+/- 0.3) suggesting an unusually small number of weaker events. The timing was highly correlated with injection with the largest events (stages 2 and 4) preceded by weaker events (ML0 and ML1.4) all located near the Preese Hall well, c. 500 meters south of the injection interval. The observed seismicity is almost certainly induced by hydraulic fracturing of the Preese Hall well. Future mitigation based on microseismic monitoring during hydrofracturing should reduce the likelihood of inducing further felt earthquakes.
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Reservoir Fluids Type Identification Using Resistivity and Sonic Logging Data in Sandstone Reservoir
By G.M. HamadaThe paper focuses on the use of shallow and deep resistivity logging data readings and presented new factor: hydrocarbon moveability factor (HCM), it is a good indicator to the hydrocarbon moveability and also recovery factor prediction and also this approach provides the water saturation values. HCM factor varies from zero to one, it indicates hydrocarbon moveability (0.25
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Analytical Investigation of the Effect of the Vertical Component of Water Oil Interfacial Tension on Capillary Number
Authors M. Nourani, T. Tichelkamp, O. Torsæter and G. ØyeMany definitions of the capillary number currently used in petroleum science neglect the contact angle or set it equal to zero by assuming strongly water-wet reservoir conditions. Nonetheless mixed-wet and oil-wet reservoirs are more common than water-wet ones. In those studies in which the contact angle or its cosine, respectively, is considered, wettability alterations are often treated independent of the water-oil interfacial tension. However, drastic reductions of the latter, which have been in the focus of studies on surfactant flooding for several years, should not be thought to leave the contact angle unchanged. Also, to the knowledge of the authors, the vertical component of water-oil interfacial tension and its effect on the capillary number have not been discussed in petroleum science by now. This value, described extensively by Kern and Müller (1991), is considered to be of some relevance in the mathematical treatment of microscopic wetting phenomena. Taking the vertical component of the interfacial tension into account, a new expression of the capillary number was derived to explain the connection between contact angle, oil-rock surface tension, water-rock surface tension and water-oil interfacial tension.
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Seismic Risk Assessment of Buildings in the Highly Populated Earthquake-Prone Areas of the UAE
By A.M. MwafyThis paper briefly discusses the methodology and preliminary results of a comprehensive research project for the vulnerability assessment of the existing building inventory in a highly populated seismically active area in the UAE. The focus is on the shoreline area from Dubai to Ajman due to its valuable building inventory, high population and vulnerability to earthquakes originated from different seismic sources. The study includes pre-code and modern multi-story buildings as well as emergency facilities due to their vital role in the recovery period following an earthquake. The building inventory in the selected study area is collected and classified, and a wide range of representative structures, ranging from 2 to 100 stories, are designed and idealized for dynamic response simulations. Extensive incremental dynamic analyses (IDAs) are conducted for the reference structures using a verified inelastic analysis platform and ground motions with increasing severity to assess the impacts of anticipated seismic scenarios. The results confirm the significance of considering different earthquake scenarios for the vulnerability assessment of the diverse building stock in the study area. The derived vulnerability functions in this study are prepared for the direct integration with a broad loss estimation system for the UAE and similar regions.
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Determination of Source Parameters of The Beni-Ilmène (Algeria) Earthquake Sequence (Mw=5.5, 5.3, and 5.3)
Authors H. Beldjoudi, H. Djellit, B. Delouis, S. Gharbi and A.K. Yelles-ChaoucheA moderate earthquake with moment magnitude Mw=5.5 hit the Subbibanique region in the East of Algeria at the locality of Beni-Ilmène on 14/05/2010 at 12h29mn(GMT).The earthquake was located by the CRAAG at latitude 35.99°N and longitude 4.19°E, the depth was 6 km.The Focal Mechanism(FM) of the seismic source obtained by waveform modeling (near-field) shows left-lateral strike-slip for the nodal plane oriented N345° and right-lateral strike-slip for the second nodal plane oriented N254°. A second shock stroke on 16 May 2010 with Mw=5.3. It is localized 9 km SW of the first shock at latitude 35.96°N, longitude 4.06°E and 5 km of depth. The FM obtained by waveform modeling shows reverse faulting with nodal planes oriented NE-SW. A third shock hit on 23 may 2010 with Mw=5.3, localized 7 km at the south of the first shock at the latitude 35.93° N, longitude 4.12° N and 6 km of depth. The FM obtained shows a left-lateral strike-slip plane oriented N355° and a right-lateral plane oriented N85° similar to that of the first shock. Geologic and sismotectonic analysis lead us to conclude that the fault plane of the first shock is oriented NNW–SSE and other shocks were generated by separate faults.
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A P-wave Seismic Reflection Study of an Intraplate Structure: The Azambuja Fault, Portugal
Authors R. Ghose, J. Carvalho, D.V. Alves and J. LeoteThe Azambuja fault is a NNE oriented fault zone located 50 Km north of Lisbon, the capital of Portugal and has been considered as a possible source of historical earthquakes. Therefore, its study is a priority in seismic hazard evaluation. It has a clear morphological signature and Miocene and Pliocene sediments are tilted eastwards and cut by steeply dipping meso-scale faults presenting reverse and normal offsets with a net downthrow to the east. Neotectonic studies indicate Quaternary slip on the fault in the range 0.05 to 0.06 milimetres/year. However, the fault has not been observed to affect Pleistocene or Holocene sediments. Here, we present a P-wave seismic reflection study carried out to image the fault below the Holocene alluvium cover southwards of the fault outcrop. We show that the fault is present below the Holocene cover as suspected and, with the aid of nearby well data, that fault segments are affecting the 14 000 year aged alluvium cover, suggesting a larger slip rate then previously admitted.
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Seismic Risk and Urbanization: The Alternatives of Prevention: Case of the City of Algiers
Authors K. Boughazi and S. RebouhSeismic risk is among the major risks that threaten our country. Actually, Algeria is located on the border of the two tectonic plates that generate moderate earthquakes at large magnitudes. The capital Algiers is considered to be the most vulnerable city of the country. Not only, it bears witness to terrible seismic disasters but it is based on six seismic faults that can move at any time. Added to this phenomenon, Algiers is facing extreme urban mutation and the Urbanization process since independence has not taken seriously into account the seismic risk factor. Indeed, the development of the city along the coast of the Bay of Algiers and its current growth towards areas of the sahel and the Mitidja as well as the degradation and aging of the built environment participated to make the capital a highly vulnerable territory, which is capable of unleashing the potential of a seismic major disaster. the present communication has not the pretention to explore the whole question of the sismeic risk of the city of algiers, but debates the question of the risk under the angle of prevention
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Seismic Loss Assessment Framework for RC High-rise Wall Buildings: Dubai Case Study
Authors W. Alwaeli, A. Mwafy, K. Pilakoutas and M. GuadagniniA complete Seismic Loss Assessment Framework for code compliant, RC high-rise buildings in medium-seismicity regions exposed to different earthquake scenarios is proposed. Dubai (UAE) is taken as a case study. Studied exposure is represented by reference structures which are categorized based on height, floor layout and lateral forces-resisting systems. The main scientific challenge is to assess the behavior and vulnerability of RC high-rise buildings with shear walls. The commonly used approach of modeling shear walls with 2-noded frame element as well as more sophisticated analytical approaches is investigated. Soil effect on nonlinear response of reference structures is studied. Calibration of the analytical tools and models is conducted by using results from full-scale tests. Large number of input ground motions are selected to reflect the anticipated earthquake scenarios of the studied area. Incremental Dynamic Analyses is curried out to identify the performance limit states and to derive vulnerability relationships to define seismic risk on building inventory. Seismic loss assessment is to be conducted by correlating the risk with direct economic losses via loss model. The results confirmed the pressing need for reliable fragility relationships to represent RC high-rise wall structures based on enhanced and verified modeling approaches.
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Contribution of Site Effects Evaluation to Seismic Risk Reduction in the Zemmouri City (Algeria)
Authors M. Djeddi, R. Bensalem, H. Medjber and F. KerbacheSite effects that correspond to the amplification of incident seismic motion by soil layers constitute a serious threat to constructions during strong earthquakes and thus raise seismic risk. Indeed, recent earthquakes show that site effects are among the main causes of damage and destruction of buildings.In this work we perform spectral ratios H/V measurements of ambient noise in the Zemmouri city (Algeria), as a part of a microzonation study. Results are presented as a map of resonance frequencies showing six (6) zones. Based on this map we propose theappropriatetype ofconstructions (number of storey) that each zone can receive in order to ovoid collapse during a future possible strong earthquake.
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Recent Microseismicity and Normal Fault Activity in the Northeastern Oman Mountains, UAE
More LessRecently available seismological data reveal NE trending microseismic activity clusters in parts of the Oman Mountains, UAE. These data and focal mechanisms are combined with surface structural data to produce a simple neotectonic model to explain the seismicity of the terrain between Fujairah and Dibba. In this area there is a series of NE-SW to N-S trending faults limited in their southwestern extension by the NW trending Wadi Ham Fault (WHF). The faults show slip histories indicating multiple use during the Cretaceous and Tertiary-recent tectonic events. Since the late Tertiary these faults have dominantly normal slip histories. They provide a tensional release mechanism for stress build-ups on the N-S Zendan Fault, which separates the Makran subduction zone from the Zagros continent-continent (Alpine) zone. The Fujairah-Dibba section is modelled as a dilatational zone associated with the southern termination of the N-S trending Zendan Fault. One consequence of this model is that the previously reported dextral and sinistral slip on the WHF may not indicate significant changes in regional principal stress orientations.
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Groundwater Level Changes as a Vital Tool in Geozoning of Al-Ain City, United Arab Emirates (UAE)
Authors A. Murad, S. Hussein, A. Aldahan, H. Baker, A. Gabr, A. Al-Saiy, W. Hashem and O. AbdelghaniCombining hydrogeological data with subsurface geological conditions represent the data base for a preliminary geozoning map of Al-Ain City, UAE. The groundwater depth data suggest a general increases outwards from the city center, which together with surface seeps indicate uprising groundwater level. The results indicated that constructors of buildings and infrastructure in most central part of the city need to pay attention to the changing situation in groundwater level and related effects on the stability of foundation substrata.
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Detailed Geophysical, Hydrochemical, Hydrogeological Studies of Western Krishna Delta, Andhra Pradesh, India
Authors S.K.G. Krishnamacharyulu, B.U.M. Rao and V.S. SinghIn coastal regions, particularly in Deltas the fresh groundwater aquifers are under stress due to the improper mining of fresh water. Groundwater studies in the Deltas are difficult mainly due to complexities in their geomorphology. Western Krishna Delta in southern India with densely populated and abundant agricultural fields is one example where the detailed hydrogeological studies are prerequisite for sustainable water management. Most of the earlier hydrogeological studies carried out were only at macro level and considered the entire Delta as one geomorphic unit i.e. alluvium. This study shows that this delta is not occurring as one geomorphic unit and there are different micro-geomorphic units in it. Keeping this in view a detailed study is carried out to identify different micro geomorphic units and groundwater conditions in each of the geomorphic unit. Dividing the Delta into micro units is mandatory in order to understand and address the groundwater problems, as each micro geomorphic unit has major bearing on the occurrence of groundwater and its quality. A comprehensive study is made using geophysics, hydrometerology, hydrogeological and hydrochemistry to understand the salinity conditions in this Delta area and to delineate the fresh water pockets in order to protect the precious groundwater resources.
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An Integrated Geophysical, Hydrogeological and GIS approach for Surface and Groundwater Management in Arid Region, KSA
Authors M. A. Raza, T.O. Idris, A.W.F. Alahmari and W.F. GalalThe water resources management in Saudi Arabia is vital aspect to address as there is no other alternative for the sustainable developments of these precious natural resources. In the Arabian shield there is an opportunity to established water management framework to assist the villagers and nomads (Bedouin’s) in their livelihoods. The study areas in wadi Tabalah and wadi Gho’ba selected as a case study of two different geological frameworks. The water resources management in Saudi Arabia is vital aspect to address as there is no other alternative for the sustainable developments of these precious natural resources. In the Arabian shield there is an opportunity to established water management framework to assist the villagers and nomads (Bedouin’s) in their livelihoods. The study areas in wadi Tabalah and wadi Gho’ba selected as a case study of two different geological frameworks.
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Application of High Resolution Electromagnetic Frequency Soundings in Mapping of Oil Contamination Flow Routes
By P.J. SaksaSmall coil separation (hand-held) electromagnetic (EM) mapping systems are frequently used in environmental and hydrological surveys. Multi-frequency capability allows shallow earth resistivity soundings to be conducted. Apparent depth of the response is approximately square root of the skin-depth value. In frequency domain true measurement accuracy and system stability factors are important because earth responses can be small in magnitude. Measurement height needs to be taken into account in absolute values and in data inversion. Case study concerns with mapping of shallow overburden variations for light (diesel) oil spill flow routes in eastern Finland. Oil contamination occurred years ago and current interest was to map potential flow routes along bedrock surface or in bedrock depressions where flow along the groundwater layer surface can happen. Survey was taken with electromagnetic frequency domain instrument. Data was interpreted with converted apparent resistivity maps, 2-layer 1-D model inversion, calculating electrical conductance maps and producing bedrock surface elevation map. Results indicate that EM surveying is useful method in detailed hydrological studies. Results were used with success to place new investigation holes and install groundwater standpipes into potential flow routes.
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Recent AEM Case Study Examples of a Full Waveform Time-Domain System for Near-Surface and Groundwater Applications
Authors J.M. Legault, A. Prikhodko, T. Eadie, K. Kwan, G.A. Oldenborger, V. Sapia, A. Viezzoli, E. Gloaguen, B.D. Smith and M.E. BestEarly time or high frequency airborne electromagnetic data (AEM) are desirable for shallow sounding or mapping of resistive areas but this poses difficulties due to a variety of issues, such as system bandwidth, system calibration and parasitic loop capacitance. In an effort to address this issue, a continued system design strategy, aimed at improving its early-channel VTEM data, has achieved fully calibrated, quantitative measurements closer to the transmitter current turn-off, while maintaining reasonably optimal deep penetration characteristics. The new design implementation, known as “Full Waveform” VTEM was previously described by Legault et al. (2012). This paper presents some case-study examples of a Full Waveform helicopter time-domain EM system for near-surface applications
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Rethink (Ground) Water Knowledge and Needs Using Airborne EM
Authors A. Menghini, A. Viezzoli and F. JørgensenIn many countries, United Arab Emirates and most of the Middle East countries included, the need for groundwater has increased and/or is bound to in the upcoming years. The Danish Government has fully understood the importance to manage and preserve groundwater for current and future generations. In 1998 it began an ambitious nation-wide groundwater mapping programme, which will be completed by 2015, and having the purpose to get an accurate picture of Danish aquifers. Geophysics plays a fundamental role, through the use of Airborne EM (AEM) and ground-based methods. Another key feature is the use of rigorous data processing and protocols, together with the use of innovative 3D geological modelling. Building on this experience, the Danish Minister of Environment supported the Rethink Water project, a network of over 50 Danish companies, organisations and institutions able to join knowledge among industry, researchers and governmental bodies in order to improve water safety and efficiency. The aim is to use this experience to propose the same approach (as a whole, or using only some of its constituent blocks) to other countries all over the World, by promoting knowledge transfer to the local partners.
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Characterization and Monitoring of Perched Aquifer (Saclay, France)
More LessPerched aquifer are often complex hydrological systems and difficult to accurately characterize. These systems could be permanent or temporary and are created usually in the subsurface in the vadoze zone above another aquifer. The most common shallow lithology in Ile-de-France (France) is loam or clay formations. Because of their proximity to the surface, they are drained to limit the disruptive effect to the development of human construction or agriculture. However, they can also prove to be a useful resource for water plants and crops in times of drought when it is located deep enough. Many tools can be used to study the characteristics and the temporal evolution of the water. Thus, in this study, the CETEs Île-de-France has equipped the area of a number of piezometers containing probes that allow measurement point taken but also a continuous monitoring of the water level subsurface (fig. 2). Associated with these methods, geophysical campaign was carried out in order to have a vision in the area of the location of water and possibly find a connection between the various water points symbolized by the piezometers. For this, the ERT (Electrical Resistivity Tomography) and multi-frequency EM methods were done.
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Hydrogeophysical Study of the Effect of AlKhod Dam on the Groundwater and Saline/Fresh Water Interface using TDEM Method-AlKhod Area, Oman
More LessOne-third of the population of Oman depends on groundwater extracted from the alluvium along the cost of the Gulf of Oman. However, groundwater depletion and seawater intrusion constitute major challenges along coastal aquifers in Oman. The objective of this study is to locate the extent of seawater intrusion and to map the shallow layer aquifer in the region where water accumulates from the rain or flooding at AlKhod dam. In order to assesses the effect of the groundwater infiltration, which recharge the aquifer and fight the seawater invasion, a quantitative approach for the groundwater quality and distribution is required to provide us with good knowledge of the spatial distribution of the aquifer thickness and the nature of sediments. Where wells and their geologic logs are not available or not deep enough, geophysical surveys should be considered due to its low cost and short acquisition time. Application of Time-Domain Electromagnetic (TDEM) method proved to be a successful in mapping the fresh/saline water interface and in locating the depth of fresh water aquifer in AlKhod area, Oman. Citation El-Kaliouby, H., [2013] Hydrogeophysical study of the effect of AlKhod dam on the groundwater and saline/fresh water interface using TDEM method-- AlKhod area, Oman. EAGE conference on engineering geophysics, Al Ain, UAE, Nov 24-27. Authors/Affiliations Hesham El-Kaliouby (1), (2) (1) Sultan Qaboos University, Earth Science Dept., Oman (2) National Research Center, Geophysics Dept., Egypt
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TEM Prospection for the Definition of the Hydrogeological Setting in a Quarry in Central Italy
Authors G. Morelli, S. Floris, G. Pagano, M. Pelorosso and S. Del GhiandaIn several parts of the World, study, evaluation and safeguard of water resources are very important topics, due to the increasing water request that is responsible for pollution’s problems and shortage of the aquifers. Therefore it is basic to define accurately the potentiality and vulnerability of the aquifers in order to plan their use and to ensure availability over time. In this case study we used the TEM method (transient electromagnetic method) [1, 2, 3] in order to reconstruct the hydrostratigraphy of a regional aquifer that could be affected by a quarry activity (basalts extraction) in Castel Viscardo, Terni, Central Italy. The main aim was to map the impermeable substratum, as a first step to define the local hydrogeological model: the survey area is characterized by the presence of permeable Pleistocenic pyroclastic and lava flows, related to the Vulsinian District activity, overlapping the sedimentary substratum (mainly clays) of Pliocenic age. We have chosen the TEM method, as the electrical response of the hydrogeological units is well resolved, as reported by Floris et al. [4]: lava and tuffs show similar resistivity, but higher than the deeper clays. The conductive response of this latter makes the methodology very suitable, as the detection of conductors is greatly enhanced by EM prospections. The interpretation of resistivity profiles, obtained from TEM soundings, allowed us to understand clearly the electro-stratigraphy contacts, related to the main hydro-lithological layers. TEM methodology is a well known tool for hydrogeology, as it is highly effective, among “the ground-based” methods: it allows to investigate down to great depths (200-300 m and more), by means of small energizing devices, without galvanic contacts with the ground and with high resolution power (mainly in the case of conductive targets), with relatively low costs. It allowed us to investigate, in short time, a relatively wide area (about 10 Km2).
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Evaluating the Water Storage Capacity of the Kharga Basin (New Valley Oasis) Using Satellite Spatial and Temporal Gravity
Authors K. H. Zahran and M. AttyaKharga Oasis is the southernmost of five oases in the Western Desert of Egypt. The Oasis bears potential Nubian Sandstone Aquifer, which considered being the most bearing underground reservoir at Egypt. Agricultural and population development of this region suggests the importance of the evaluation of its water storage capacity. Satellite spatial and temporal gravity data have opened new perspectives on the Earth sciences and hydrological studies. The two sets of the satellite data have been utilized to study configuration and temporal water recharge capacity of underground basin reservoirs. The study shows set of faulting led to a complicated configuration of the underground sand basin. In addition, Monthly data from GRACE estimate the irregularities of the water income. Finally, the study pointed out the potentiality of using satellite spatial and temporal gravity data to study configuration and temporal water recharge capacity of underground basin reservoirs.
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Evaluation of Laboratory Schmidt Hammer Tests on Carbonate Rocks
Authors H. Arman, W. Hashem, O. Abdelghany and A. AldahanBeing quick, inexpensive, non-destructive and handy, the Schmidt Hammer (SH) test has been widely used to determine hardness and to predict the unconfined compressive strength (UCS) of rocks. However, a review of empirical equations recommended for determination of the USC of rocks based on the SH rebound number (N) suggests that one unique formula cannot be representative for all types of rocks. Even though the obtained relationship is a useful and quick reference to assign a preliminary value for UCS, geological features such as composition, texture and mineralogy influence the mechanical properties of rock masses and these factors should be carefully evaluated. In the work presented here, a case study was chosen to demonstrate and discuss the effectiveness of particular geological circumstances on laboratory SH test results concerning different carbonate rocks. Three different types of limestones, chalky, marly and dolomitic are available in the Tertiary carbonate sequence at the studied area which is Jabal Hafit, south of Al Ain city, United Arab Emirates (UAE). The results clearly show that rapid changes in carbonate rocks composition, texture and mineralogy always create problems in generalizing the mechanical properties which are essential parameters in geological and engineering practices.
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Contribution of Electrical Tomography Methods in Estimating Slope Stability at Mavropigi Lignite Open Pit Mine, Northern Greece
Authors H. Hamdan, A. Vafidis, Z. Agioutantis and E. SharifThis case study presents the results of a geophysical survey, where 2D and 3D Electrical Resistivity Tomography were employed to evaluate the stability of surface lignite mine's slopes. Specifically, it took place in the Mavropigi lignite open pit mine, Northern Greece, where fracture zones and discontinuities have been recently observed close to the boundaries of the pit, raising concerns about the stability of the pit walls. A geophysical survey was part of an extensive geotechnical investigation program conducted in order to investigate the conditions of the area. Synthetic data were initially generated in order to help plan an efficient electrical tomography survey, in a region with complex geology and irregular terrain. Finally the geophysical survey provided invaluable data regarding the geometry of the bedrock, which was essential for the slope stability calculations.
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Structural and Stratigraphic Parameters as Tools for the Geozoning Project of Al-Ain City, UAE
Authors W. Hashem, O. Abdelghany, A. El Saiy, A. Murad, S. Hussein, A. Gabr, H. Baker and A. AldahanRapid urbanization dramatically increases the demand for land that requires planning and zoning which allow the authorities to achieve safe, manageable and sustainable construction expansions. Geozoning represents an effective way of summarizing surface and subsurface land stability that can be used for setting out regulations for construction purposes. We present here a preliminary geozoning survey of Al Ain city as a first stage to build-up a database which divides the city into several stability zones.
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Monitoring Small land Subsidence Phenomena in the Al-Ain Region by Satellite SAR Interferometric Stacking
Authors A. Cantone, P. Riccardi, H.A. Baker, P. Pasquali, D. Closson and N. Abou KarakiSome areas of the United Arab Emirates suffered from subsidence, cavities and related problems,[0]. Subsidence and, in general, surface land deformations and displacement phenomena, typically involve large regions in the geographical meaning. For such regions, in principle, the terrain displacements should be monitored with an accuracy that is in the orders of magnitude smaller than the spatial resolution: one measurement every several meters should bring an accuracy of few centimetres or even millimetres. Not many technologies can nowadays provide such a combination. One of the few is Synthetic Aperture Radar Interferometry, and all related developments, that can, generally, be identified as Advanced Interferometric or Interferometric Stacking techniques. This paper presents one case study in Al-Ain region (UAE) by exploiting Interferometric Stacking techniques to monitor land displacements in the order of few millimetres per year.
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Data Quality Weighted Seismic Traveltime Tomography
Authors T. Fechner, L. Karl, M. Kunert and D. TweetonSeismic tomography is believed to be the seismic method promising highest accuracy and reliability. Remaining uncertainties due to a non-zero residual error in fitting the traveltime data are often neglected. We present a numerical implementation of traveltime data weighting into the well-known SIRT algorithm which provides a more reliable velocity determination on one side and a data weight or uncertainty image including a residual error map on the other side. The data weighting allows the in-cooperation of individual data quality criteria to influence the inversion procedure and to allow a non-equal weighting of the traveltimes within the tomographic inversion. By choosing appropriate weighting factors the seismic velocities recovered during the inversion process are more realistic compared to results obtained using equal-weighted traveltimes. The data quality weighted inversion has been tested on different synthetic data sets. The additional information provided by the new approach along with the seismic velocity tomogram may support the geophysicists interpretation of a seismic tomogram.
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Application of K-means Algorithm to Two-dimensional Electrical Resistivity Imaging
Authors K.S. Ishola, M.N.M. Nawawi and K. AbdullahThis paper describes the application of unsupervised classification using k-means algorithm to combine and classify two-dimensional (2D) inverse resistivity models arising from the use three different electrode arrays for resistivity imaging. The 2D inversion results obtained were used as the input images for the classification scheme. The k-means algorithm classified the synthetic models each into sixteen (16) clusters, each cluster associated with three mean resistivity vectors from each electrode array. The resistivity values were assigned to each cluster employing basic statistical approach. An evaluation of the classified images was performed by comparison with the resistivity values between classified and true models. This was further confirmed by estimation of the mean absolute error for each image. The results of comparison of resistivities and the estimated error show that maximum approach give the best representative of the real models than using individual apparent resistivity. Keywords: Unsupervised classification, inverse resistivity model, k-means, clusters, accuracy assessment, classified image
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A Hybrid Occam and Marquardt-Levenberg Inversion Approach to Time-lapse Transient Electromagnetic Monitoring of Water Infiltration at a Recharge Basin
Authors A. Swidinsky and H. El-KalioubyRecharge flux is one of the most difficult components of the water balance to measure. However, quantitative estimates of this flux are critical for water resource planning in semi-arid and arid areas. Electrical and electromagnetic methods may be useful for monitoring recharge because of their dependence on the electrical conductivity of sediments and therefore on the volumetric water content of a porous medium. In this study, we examine transient electromagnetic (TEM) methods for monitoring water infiltration into an initially dry soil and subsequent drainage of the wetting front with time at a recharge basin near Tucson, Arizona. To produce geologically reasonable subsurface conductivity images from a real TEM dataset, we suggest a hybrid time-lapse inversion approach consisting of a smooth Occam inversion for the baseline day, followed by Marquardt-Levenberg inversions for the subsequent monitor days. Such an approach is uncommon in conventional electromagnetic inversions but in our case is useful in emphasizing subsurface changes during a monitoring experiment. Results suggest an impermeable clay layer at approximately 30m depth and a subsequent buildup of water in the subsurface to the west of the site.
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Geological, Geotechnical and Geophysical Conditions Encountered at Three Distant Sites Across Abu Dhabi Emirate, UAE
Authors S. Parashar, P. Asprouda, H. Al Hammadi and J.D. LeeDetailed subsurface investigations were conducted at three distinct sites, extending to depths exceeding 100 m and involved large number of boreholes coupled with a suite of surface and subsurface geophysical measurements and laboratory testing to properly characterize the subsurface conditions. The paper presents the typical subsurface conditions at each site along with geotechnical and geophysical properties of subsurface materials encountered. Further, an approximate geological and geophysical cross section is postulated based on the subsurface conditions encountered at these distantly located sites. Comparison of typical geotechnical and geophysical properties of subsurface material is also attempted.
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Comparison of Safe Bearing Capacity Obtained by Various Formulae for Railway Track Route ( An example of Turkey)
Authors S. Goren and K. GelisliIn this study, the factors which reeffected the mechanism of bearing capasity were summarized. The whole data were evaluated according to bearing capasity analyses which developed depend on shear wave velocity (Vs) , standart penetration test (SPT(N1)60) and mechanical tests. The data which are needed for bearing capasity analyses were collected from Sivas-Erzincan region of TURKEY. The data were reassessment which obtained seismic cross-sections, vertical electric soundings and mechanic drilling studies have made in Sivas region. These geotechnical sections were composed by making relations. The use of seismic geophysical method has been investigated, in order to detection of accurate railways, it was built in 2007 within Sivas - Erzincan boundaries were examined by Republic of Turkey Ministry of Transport in the study. Parameters of bearing capasity are calculated by Matlab. It was determined P wave velocity (Vp), S wave velocity (Vs), density (d), shear modulus, elasticity modulus, bulk modulus, poisson ratio, soil bearing capacity parameters.
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Application of Geophysical Measurements for Geotechnical Analysis – Foundation Settlement
By E. SharifThe assessment of the likely foundation settlement of giant oil storage tanks posed a great challenge. The proposed tank farm is located in Fujeira in UAE on reclaimed off-shore ground with rockfill. The depth of rock fill ranged between 5m to 16m above the sea bed to create a level platform. The rock fill is composed of large stones and rock fragments with sizes ranging between < 1 Kg to 1000 Kg, and was dumped on the sea bed without any treatment / densification.
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Overview of the Structural Pattern in Northern Tunisia Inferred Gravity Interpretation
Authors I. Hamdi Nasr, A. Amiri, M.H. Inoubli, K. Sebei and H. Boussiguame zone in the Atlassic region. The gravity analysis consists in mapping the contrasting gravity responses: complete Bouguer anomaly, residual anomaly and derivative maps and Euler Deconvolution. The main results display a positive amplitude gravity anomaly as the response of Triassic evaporite bodies and important NE–SW-trending features at the boundaries between the Triassic outcrops and their enveloping strata. In contrast with gravity calculations of a salt dome structure usually resulting in negative gravity anomaly models, they express a positive gravity anomaly generated by a higher density of the Triassic mass contrasting with a lighter Meso-Cenozoic rock envelope. Gravity lineaments allow distinction of alignments extending NE-SW, which retrace master fault systems bordering the Triassic masses; the contact between Triassic and Cretaceous systems (or more recent), correspond to a part of steep gravity gradient. These faults are thought to have given issue to ascending evaporite-bearing masses.
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Use of Accoustic Televiewer in Discontinuity Characterisation for Rock Slopes and Under Ground Excavations - A Case Study
Authors M.J. Ahmed and M. HarbThe paper discusses the technique for quantifying and analyzing the geometry of joint patterns developed using conventional empirical technique of stereographic analysis/ kinematic admissibility check/ markland’s test and its confirmation with the results of acoustic televiewer logs for characterization of rock mass discontinuities during investigation for some rock cut slopes and tunnels in the United Arab Emirates. The Acoustic televiewer study is relatively a new technique for characterization of discontinuities with more precision on the azimuthal orientation, depth and thickness of the discontinuities. The results can be correlated with bore logs and the surface empirical method of stereographic analysis to get a more precise and dependable interpretations during the investigation for rock cut slopes and underground excavation projects. The technique was applied to over 30 m deep rock cut slopes and nine large diameter (+10 m) tunnels in the UAE and found to be beneficial.
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The Applications of Forensic Geology & Geophysics for Police and Law Enforcement Ground Searches
By L. DonnellyA ground search may be defined as; ‘The application and management of systematic procedures and appropriate detection equipment to locate specified targets’ (UK, Association of Chief Police Officers). Ground searches may be conducted to locate missing persons, homicide graves, no-body murders, recover evidence and concealed items to support a prosecution, gather intelligence, deprive criminals of their resources and opportunities to commit crime, protect vulnerable targets or to assist with search and rescue. The objective of this paper is to provide an overview of the applications of forensic geology and geophysics for ground searches. This paper also seeks to reach out to new audiences in the United Arab Emirates and Middle East region, who may be considering the deployment of geophysics to assist with ground searches.
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Geoforensic a New Significant Tool in Crime Investigation for the UAE Legal System
Authors S. A. Al Katheeri, A. El Saiy, A. Aldahan, K. Al Naimi and A. Al KaabiTextural and mineralogical composition of soil materials were used as geoforensic tool to support legal evidence in a case where a child was murdered by a car impact in Abu Dhabi. The data revealed strong link between the soil samples collected from the car and from the crime site. These geoforensic indicators support the accused person story regarding possible throwing of soil materials toward the car by the children.
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