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- Volume 32, Issue 8, 2014
First Break - Volume 32, Issue 8, 2014
Volume 32, Issue 8, 2014
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Geophysical investigation in the Temple of Poseidon at Cape Sounio, Attica, Greece
Authors G. Apostolopoulos, K. Leontarakis and C. OrfanosG. Apostolopoulos, K. Leontarakis and C. Orfanos present an integrated geophysical investigation of the Temple that has been done with EM, GPR and ERT measurements. The cliff at Cape Sounion is the spot from where Aegeus, King of Athens, leapt to his death, thus giving his name to the Aegean Sea. The original Archaic Period Temple of Poseidon on the site, which was built of tufa, was destroyed in 480 BC by Persian troops during Shahanshah Xerxes I’s invasion of Greece. After the Athenians defeated Xerxes in the naval Battle of Salamis, the later Temple at Sounion, whose columns still stand today (Figure 1), was probably built in ca. 440 BC. This was during the ascendancy of Athenian statesman Pericles, who also rebuilt the Parthenon in Athens. The Ministry of Culture’s 2nd Ephorate of Prehistoric and Classical Antiquities has set up a project for geophysical investigation to detect whatever constructions or material may exist under the temple (possible relics of the previous temple). This project has been undertaken by the Applied Geophysics Laboratory of the School of Mining and Metallurgical Engineering at the National Technical University of Athens.
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Combined onshore and offshore seismic investigations image fault structure at the geothermal field of Aedipsos-Yaltra, central Greece
Authors V. Karastathis and E. MouzakiotisVassilis K. Karastathis and Evangelos Mouzakiotis delineated the hydrothermal mechanism associated with a large fault indicating the best exploitation point. The region of Aedipsos in the northern part of Evia island (Euboea), Greece (Figure 1), has been famous for its hot springs since the 4 th -century BC. It is notable that there was an ancient legend claiming that Hercules used to bathe in the hot waters of Aedipsos to renew his strength after his labours. Those springs have also been referred to by ancient writers such as Aristotle, Strabo, Plutarch, Claudius Ptolemaeus. The Roman general Syllas also visited Aedipsos and built public baths at the place. Today the region is a touristic attraction due to its thermal springs. The Yaltra Baths (or Gialtra), situated only 5 km to the west, also have high touristic development based on the local thermal springs. The hot springs of the wider region can be seen in Figure 1. In several sites the temperature of the springs reaches values higher than 40 o C and up to 84 o C (Gioni-Stavropoulou, 1983).
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Application of empirical mode decomposition methods to ground penetrating radar data
Authors M. Manataki, A. Vafidis and A. SarrisM. Manataki, A. Vafidis and A. Sarris compare empirical mode decomposition methods using both synthetic and real GPR data. Empirical Mode Decomposition (EMD) is a relatively new technique introduced by Huang et al., (1998) for analysing non-linear and non-stationary time series. The decomposition is based on a signal’s local extrema, which define different oscillation modes present in the signal. What EMD does is the separation of those different oscillatory modes into a finite and usually small number of stationary sub-signals called Instrinsic Mode Functions (IMFs). EMD suffers from mode mixing which limits the frequency separation among the different modes and makes the physical meaning of the IMFs unclear.
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Ground-based archaeological prospection: Case studies from Greece
Authors N. Papadopoulos, G. Tsokas, A. Sarris, P. Tsourlos and G. VargemezisNikos Papadopoulos, Gregory Tsokas, Apostolos Sarris, Panagiotis Tsourlos and George Vargemezis assess the preservation of standing monuments and ancient water management facilities. Archaeological prospection or archaeogeophysics includes the diverse geophysical methods employed either in planned excavations to guide the archaeological research in advance of and during the excavation process or in salvage excavations to provide a rapid assessment during the development of infrastructure in urban or rural environments. On a more general basis, these techniques are also applicable to support regional archaeological surveys by locating areas of archaeological interest and contributing to the settlement pattern analysis (Sarris and Jones, 2000). Unlike the destructive nature of the archaeological excavations, geophysical prospection techniques are non-invasive, providing at the same time a rapid reconnaissance of a site without disturbing the ground or the monuments themselves. The success or the failure of these techniques strongly depends on the contrasting physical properties that exist between the archaeological buried targets and the hosting material.
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A multi-physics approach to near-surface characterization over the Marcellus shale
Authors H. Snyder, C. Beasly, C. Friedemann and C. KincheloeHorace Snyder, Craig Beasley, Chris Friedemann and Carl Kincheloe discuss a multi-physics approach to identify, map and characterize surface and near-surface features in support of environmentally sound E&P operations. Oil and gas activities in the Appalachian Basin have increased dramatically in the past decade as E&P operators have invested billions of dollars to develop the Marcellus and Utica unconventional shales that both underlie large portions of the states of Pennsylvania and Ohio. The Appalachian Basin typifies an active hydrocarbon system, with both oil but especially natural gas continuously migrating toward the surface, even in the present day, along naturally occurring fault systems and fracture networks. The basin is also populated by tens of thousands of wellbores – many of which are not logged in public records – that were drilled by both commercial E&P operators and the general populace over the past 150 years. In some areas, naturally migrating gas has been trapped in shallow structures, representing both a potential secondary target but also a geo-hazard for E&P operators who might encounter them en route to the Marcellus and Utica reservoir targets. To identify, map and characterize these surface and near-surface features in support of environmentally sound E&P operations, a multi-physics methodology was utilized. A combination of airborne magnetic, hyperspectral and electromagnetic (EM) measurements were acquired, integrated and simultaneously interpreted to locate surface hydrocarbons, fault systems, orphaned wellbores and trapped shallow gas pockets.
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DC geoelectrical methods applied to landfill investigation: case studies from Greece
Authors P. Tsourlos, G.N. Vargemezis, I. Fikos and G.N. TsokasP. Tsourlos, G.N. Vargemezis, I. Fikos1 and G.N. Tsokas present four case studies of geoelectrical methods to investigate different types of landfills in Greece. There is a growing demand for monitoring both operating and rehabilitated municipal solid waste (MSW) landfills. In this framework, geophysical investigation and particularly geoelectrical techniques are considered as a valuable tool in environmental management. The DC geoelectrical methods are probably the most popular geophysical techniques applied to landfill investigations (Meju, 2000). The conductive signature of the leachate renders geoelectrical methods ideal for the investigation of active or decommissioned landfills with respect to mapping their structure (i.e., shape, size) as well as for locating potential leakage and migration of leachate into the deeper geological layers. A large number of relevant studies can be found in literature, among others: Cartwright and McComas, 1968; Klefstad et al., 1995; Barker, 1990; Carpenter et al., 1991; Binley et al., 1997; Stanton and Schrader 2001; Karlik and Kaya, 2001; Porsani et al., 2004.
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Signal enhancement and geometric information retrieval from 2D GPR data with multi-scale, orientation-sensitive filtering methods
By A. TzanisAndreas Tzanis discusses denoising GPR data and retrieving geometric information with advanced scale-and-orientation-sensitive filtering methods. Ground Probing Radar (GPR) is an almost indispensable means of imaging near-surface structures and enjoys a very diverse and broad range of applications. Two-dimensional GPR images of the subsurface frequently contain geometric information from small scatterers (diffraction hyperbolae) as well as dip-dependent information from dipping reflectors such as geological bedding, structural interfaces, cracks, fractures, joints, empty or filled cavities associated with jointing or faulting and other conceivable structural configuration. The second group of targets, especially fractures, are usually not good reflectors and are spatially localized; in geological, geotechnical and engineering applications their detection is frequently a primary objective. At the same time, GPR is notoriously susceptible to noise. An innumerable variety of natural and artificial buried objects can cause unwanted reflections and scattering. Anthropogenic noise is worse and includes reflections from nearby structures, interference from power lines and telecommunication devices etc. This type of noise is only partially countered with shielded antennae while the extraneous or reflected airwaves, critically refracted airwaves and groundwaves are not easily suppressed during acquisition. Finally, there’s systemic noise, frequently manifested as ringing (antenna self-clutter). In many cases, the noise has definite geometrical characteristics (e.g., high-angle crossing clutter). Because the GPR source wavelet is tuned at a single frequency, the information returned by the subsurface structure is usually limited to a relatively narrow band around it and the rest of the spectrum is swamped in noise. Raw GPR data usually require post-acquisition processing, as they provide only approximate target shapes and depths.
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Seawater intrusion imaging at Tybaki, Crete, using geophysical data and joint inversion of electrical and seismic data
A. Vafidis, P. Soupios, N. Economou, H. Hamdan, N. Andronikidis, G Kritikakis, G. Panagopoulos, E. Manoutsoglou, M. Steiakakis, E. Candansayar and M. Schafmeister present the processing and interpretation of data to show seawater intrusion imaging. Coastal areas are densely populated, since they provide the best conditions for both economic development and quality of life. One of the most important environmental problems in coastal areas is the salinization of ground water. The dynamic hydrogeological balance between freshwater and seawater in coastal aquifers is subverted by groundwater over-pumping that lowers the groundwater level and causes seawater movement into the coastal aquifers (Abdalla et al., 2010). In arid or semi-arid areas, where the rainfall is the main source of freshwater and the groundwater is inadequate, the problem of seawater intrusion is irreversible leading to the conclusion that effective prediction tools are of vital importance for the prevention of aquifer contamination.
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Comprehensive mapping of landslide dynamics by nanoseismic monitoring
More LessMarco Walter and Manfred Joswig present the mapping of key dynamics influencing deepseated mass movements by applying nanoseismic monitoring at a mudslide in the French Alps. Slope-related failure by fracture processes with magnitudes of ML < 0.0 has been observed on rockslides by classical seismological monitoring techniques. Fracture signals at rockslides were monitored by e.g,. Roth et al. (2005) at the Aknes fjord in Norway, Brückl and Mertl (2006) in the Austrian Alps, Spillmann et al. (2007), in the Swiss Alps, for a rockslide by Helmstetter and Garambois (2010), and for a detaching rock column by Levy et al. (2011), both in the French Alps. In contrast to the aforementioned studies, we present the seismic analysis of softrock-landslide dynamics observed at the mudslide in Super-Sauze, French Alps (Walter et al., 2009, 2012). Like Super-Sauze, most softrock landslides are geomorphically classified as creeping, thus the existence of measurable signals caused by brittle deformation could not have been expected. The apparent contradiction of viscous creep coexisting with brittle deformation on softrock landslides resembles crustal-scale tectonics where aseismic creep coexists with earthquakes (Peng and Gomberg, 2010). Already in 1995, Gomberg et al. proposed the term ‘slidequake’, which describes the fracturing or stress relief of slope material by means of brittle failure.
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Volumes & issues
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Volume 42 (2024)
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Volume 41 (2023)
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Volume 40 (2022)
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Volume 39 (2021)
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Volume 38 (2020)
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Volume 37 (2019)
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Volume 36 (2018)
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Volume 35 (2017)
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Volume 34 (2016)
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Volume 33 (2015)
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Volume 32 (2014)
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Volume 31 (2013)
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Volume 30 (2012)
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Volume 29 (2011)
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Volume 28 (2010)
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Volume 27 (2009)
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Volume 26 (2008)
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Volume 25 (2007)
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Volume 24 (2006)
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Volume 23 (2005)
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Volume 22 (2004)
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Volume 21 (2003)
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Volume 20 (2002)
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Volume 19 (2001)
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Volume 18 (2000)
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Volume 17 (1999)
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Volume 16 (1998)
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Volume 15 (1997)
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Volume 14 (1996)
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Volume 13 (1995)
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Volume 12 (1994)
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Volume 11 (1993)
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Volume 10 (1992)
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Volume 9 (1991)
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Volume 8 (1990)
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Volume 7 (1989)
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Volume 6 (1988)
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Volume 5 (1987)
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Volume 4 (1986)
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Volume 3 (1985)
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Volume 2 (1984)
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Volume 1 (1983)