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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
21 - 40 of 71 results
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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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