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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
41 - 60 of 71 results
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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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Collaborative Geophysical Monitoring of Simulated Forensic 'Crime Scenes’ in the U.K.
Authors J.K. Pringle, J.P. Cassella, A. Williams, P. Cross, A. Ruffell and P. MastersThis paper provides an overview of current collaborative academic forensic geophysics research on various U.K. test sites to detail the importance of forensic simulated burial sites for forensic search investigators. Academic forensic test sites contain a variety of buried material objects that have been buried for various periods. The team also have access to historical burial grounds for data collection if required. Research is gaining an understanding of optimal search technique(s) for different buried targets, optimum methodologies and sequential search workflows. From this research, additionally a detailed understanding of the local depositional environment(s), particularly soil type(s), age/style of burial and local climate datasets are critical to have a successful detection. Ongoing long-term monitoring efforts are detailing optimal time windows for searches and techniques.
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Missing Persons Search: A Multidisciplinary Analysis
Authors A. Berti, L. Ripani, G. Braccesi, S. Bartolozzi, V. Scavongelli and G. MicheliMissing persons search is a complex and articulated activity that is performed using scientific investigation techniques. Research can be pursued with dog rescue units and geophysical surveys. The use of dogs is versatile and consent a rapid investigation of large areas. It implies years long working protocols on different dog breeds, that involve testing on both simulations and real missing persons search.
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Optimal Geophysical Techniques and Configurations for Below-Patio Forensic Targets
Authors J.K. Pringle, J.D. Hansen and C. BannerThis paper details forensic geophysical results of a study looking into below-patio targets, including metallic decommissioned ordnance and weapons and a simulated clandestine burial of a murder victim. Surprisingly metal detectors were not successful to find all near-surface buried objects, with the magnetic susceptibility technique deemed optimal at 0.25 m x 0.25 m sample point spacing. Repeat multi-frequency GPR datasets over the simulated clandestine burial found mid-frequency (225 MHz) antennae optimal to resolve the buried target, although all frequencies had significant attenuation from the patio itself. The two year GPR monitoring project of the clandestine burial found optimal time post-burial to conduct a survey was from burial up to 12 months post-burial and especially during winter months. 3D GPR datasets did not have a clear advantage over interpretation of simple 2D transects, although there were significant numbers of non-target anomalies imaged.
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Modern Trace Evidence Analysis and its Application to the Forensic Study of Soil, Sand and Dust
By S. PalenikThe basis for the forensic examination and analysis of microscopic trace evidence is stated in Locard’s Exchange Principle : Whenever two objects come into contact there is always a transfer of material between them While the amount of matter transferred may be small (and even undetectable by currently available methods) and the decay rate (i.e., loss of transferred matter over time) may be rapid, the exchange of matter during contact will nonetheless occur. The truth of this principle has been proven by research and casework, most of which was conducted during the last half of the twentieth century. It is one of the few scientific principles that forensic science can call its own since there is rarely a need to establish that two objects have come into contact in any other area of important scientific research.
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The application of Geophysics in forensic investigations
By P.L. MastersThe application of Geophysics in forensic investigations is becoming more widely accepted as a way of recovering the buried remains of clandestine burials. Some police forces in the UK now use geophysics as part of their search and location tool kit to locate clandestine burials. However, in recent times the use of geophysics in forensic investigations has become over reliant in the use of one technique, Ground Penetrating Radar (GPR). This paper will address this issue and provide case studies of where other techniques have been used to locate clandestine burials.
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Developing the Forensic Applications of the Organic Component of Sediments
Authors R. Morgan, G. McCulloch and K. ScottIt is well established that geoforensic evidence can make a valuable contribution to a forensic investigation in criminal proceedings. The physical, chemical and biological components of sediments can all offer highly environmentally specific indicators that can aid the comparison of samples recovered from relevant locations and/or exhibits, and indeed offer an indication of the provenance of the sediment. Whilst there has been a growing body of research addressing the capabilities of the physical and chemical components of sediments (and to a large degree the pollen constituent) in addition to developing improved methods of recovery and analysis, there has been less attention focussed on other biological components that can be present and the organic signatures of sediments. This paper presents research that has been carried out to assess the ability of this underutilised component of soil/sediment samples to provide meaningful and valuable intelligence and evidence to an investigation.
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The UK Police Service Approach to Specialist Search: Structure, Training and Capability of Search Assets
By C. HopeThe Police Service in the United Kingdom has a well-established and very effecive program of training in specialist search planning and management. This training, together with the development and application of technical search assets and deployment methodologies, has been fundamental to the delivery of highly effective search operations in numerous operational arenas over many years. Whilst these methodologies were initially and primarily developed to defeat the threat from terrorism, the use of these and other techniques are now widely and effectively used in the search of the ground to locate buried items and objects that may include for example; missing persons, the graves of murder victims, the location of the remains of no-body murder victims, to recover evidence and concealed items in support of a prosecution, to gather intelligence, and to deprive criminals of their resources and therefore reduce the opportunity to commit crime.
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The UK Home Office (Centre for Applied Science & Technology): Support to the Police Search Community. Specialist Ground and Marine Search Technology
By M. FergusonThe Centre for Applied Science and Technology (CAST) provides support for United Kingdom (UK) police operations and frontline delivery through the application of science and technology. The CAST Search Support team comprises a Search Technical Manager supported by highly trained, professional and experienced scientists and engineers from various backgrounds. This team provides bespoke ground search solutions, often at very short notice, to the security and law enforcement agencies across the UK. CAST also provides the rapid deployment of specialist teams to assist with locating missing persons, either underwater or on land. These searches may use geophysical equipment that includes sonar, magnetometers and ground penetrating radar (GPR). The CAST team has had particular success in finding missing persons in water using both side scan and 360o sector sonar systems. This team also works in close collaboration with the various regional police dive teams in this respect. The deployment of marine geophysical techniques has many advantages. For example, this saves significant amounts of time spent on costly underwater searches, since a large search area may belimited to a few potential targets by the marine geophysics, which can then be investigated by divers.
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The Application of a Blend of UK Police Service Assets in a Specialist Search
By G. PeffersThe object of this abstract is to provide an overview of the role of the Police Search Advisor (PolSA), how they interact with geologists, botanists and forensic archaeologists and to demonstrate the pragmatic deployment of search assets and techniques ‘in the field’, in other words how they actually “search”. The role is in fact that of a manager and was established in 1984 based on the role of a Royal Engineer Search Advisor. (The historical development of the PolSA role is dealt with in more detail in a paper submitted by my colleague Inspector Colin Hope) A PolSA is responsible for the planning, organisation, management and control of Counter Terrorism, Crime and Missing Person searches and advising senior officers on search related matters. (Association of Chief Police Officers, 2011)
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Environmental Managment of Drilling Wastes
By A.M. ShaikhDrilling waste is a complex mixture of chemicals and cuttings use to meet the diverse requirements of drilling operation, and achieve well stability throughout exploration and production activities. The developments of best available technology (BAT) and best environmental practice (BEP) techniques have improved the environmental achievements of exploration and production activities. The cutting re-injection (CRI) technology is one of the latest waste disposal techniques. Slurrification is one of the integral parts of CRI for subsurface injection of drilling waste. In this paper, few of the major environmental management techniques for drilling wastes are highlighted including major aspects of CRI technology.
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