George Vargemezis | Aristotle University of Thessaloniki (original) (raw)
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Papers by George Vargemezis
25th European Meeting of Environmental and Engineering Geophysics, 2019
8th Congress of the Balkan Geophysical Society, 2015
In this work we present the results of the application of the electrical resistivity tomography (... more In this work we present the results of the application of the electrical resistivity tomography (ERT) technique into the mapping of the fissures that appeared in the Valtonera area (Amyntaion Munisipality, NW Greece).The results of ERT provide a satisfactory explanation to justify the expression of surface cracks in specific areas and this approach can be used to provide areas that are likely to be associated to fissures in the future.
Archaeologia Polona, 2015
The Bronze Age settlement of Akrotiri on the Greek island of Santorini/Thera was covered by thick... more The Bronze Age settlement of Akrotiri on the Greek island of Santorini/Thera was covered by thick layers of volcanic pumice during the massive eruption of the Thera volcano in approximately 1613 BC. Archaeological excavations conducted since 1967 have revealed the archaeological remains of an affluent prehistoric society, living in up to three-storey-high buildings that were richly decorated with vivid frescoes and furnished with sophisticated sewer systems. To date, three buildings have been excavated completely and approximately seven buildings have been partly uncovered in an area measuring some 90 m by 120 m (Doumas 1983). Archaeological excavation at Akrotiri inevitably exposes the archaeological remains and often fragile prehistoric architecture to the risk of destruction in case of stronger seismic events, which are very likely to occur at some point in the future, since the site is located in one of the world's seismically most active regions (Chouliaras et al. 2012), being located on an active volcano. Additionally, gradual decay caused, for example, by mud wasps and accidental damage threatens with the collapse of exposed architecture at this unique site. While it is impossible to prevent partial or total destruction of the excavated architecture in case of a larger earthquake, and while the long-term preservation of this cultural heritage is an extremely difficult challenge, it is possible to document the site digitally in three dimensions and in great detail. In 2013 and 2014, the LBI ArchPro documented the excavated areas in very high resolution, using laser scanning and latest photogrammetric methods. Within this project, which has been supported by the Conservation Trust of the National Geographic Society, additional geophysical archaeological prospection techniques have been tested in the vicinity of the archaeological site of Akrotiri in order to evaluate their potential to map still buried archaeological remains without exposing them to the risk of destruction. With exception of the location Kokkino Vouno (Red Mountain) west of the archaeological site, all other nearby areas are covered by more or less thick layers of volcanic ash and pumice, rendering the application of standard near surface geophysical archaeological prospection approaches challenging. The volcanic geology and the mostly large distance between the surface and the target structures renders the use of the otherwise commonly used magnetic prospection method less than promising. Early magnetic measurements were conducted in the area by Dr. Elizabeth Ralph from the university of Pennsylvania Museum in 1967 using a caesium magnetometer, still prior to the substantial archaeological discoveries made by Spyridon Marinatos (Mavor 1969).
Proceedings, 2016
Infiltration of rainwater is of major importance for old waste disposal sites where production of... more Infiltration of rainwater is of major importance for old waste disposal sites where production of leakage is taking place even after reclamation. In this work we present an ERT monitoring case study in a reclaimed Derveni Landfill. Previous studies in the area showed that important amount of water flows within the waste volume or by lateral groundwater flow or by direct infiltration of rainwater. Maag permeability measurements showed differential behavior of the top soil. Thus, geophysical monitoring of resistivity changes during injection of known conductivity water in high resolution 2D and 3D tomographies has been applied in two selected sites according permeability distribution map. 4D inversion of 2D and 3D data sets showed the flow paths of the injected salty water within the top soil up to the depth of almost one meter. At the same time increase of the resistivity has been observed deeper than one meter that cannot be easily explained. A possible explanation, except the case of disturbed current flow which could lead to artefacts, could be the biogas flow that is interrupted by the water cap of the injection. Both explanation are to be examined as a next step to the integration of the geoelectrical monitoring.
2017 9th International Workshop on Advanced Ground Penetrating Radar (IWAGPR)
In this work we study part of the Northern wall structure of the Heptapyrgion fortress of Thessal... more In this work we study part of the Northern wall structure of the Heptapyrgion fortress of Thessaloniki (UNESCO monument) that was identified to face moisture and structural problems. Moisture damage is a critical issue in the preservation and integrity of historic walls, thus it is necessary to detect it and to develop restoration plans. Heptapyrgion is one of the most important monuments in Thessaloniki so it is very crucial to use non-destructive techniques. To achieve that, a pilot GPR survey was conducted. The data obtained with 250 and 500MHz antennas were processed and interpreted in relation to the existing problem. To further assist the interpretation 2D GPR model simulations were carried out. GPR data was also compared to geoelectrical ERT data obtained at the same section on the wall. Overall GPR images are in good agreement with existing information and proved very useful in accessing the wall structure.
Abstract: The use of two geophysical methods in the investigation of the geological setting in th... more Abstract: The use of two geophysical methods in the investigation of the geological setting in the area of a dam foundation is presented in this study. The seismic method was used in order to map the structure of the upper layers near the riverbed. VES and resistivity tomographs were also carried out. The depth to the basement was estimated by interpreting the VES curves. Interpretation of the topographic images, along with the inferred models from the seismic data, revealed the thickness of the colluvial deposits.
ArchéoSciences
– Resistance and magnetic mapping, ERTs and aerial photography put together. – Fusion was attempt... more – Resistance and magnetic mapping, ERTs and aerial photography put together. – Fusion was attempted through curvelet transform. – The useful information of all methods is given in a combined image at the site of Philippi in Greece.
Bulletin of the Geological Society of Greece
This work describes the installation and preliminary measurements of an electrical resistivity to... more This work describes the installation and preliminary measurements of an electrical resistivity tomography (ERT) system to monitor the injection of recycled water into a confined aquifer in the area of Sindos. The aim is to provide, through time-lapse electrical resistivity tomography (ERT) measurements and processing, geoelectrical images of rather increased volumetric sampling around and between the holes and to obtain improved understanding of the flow and transport of the injected water. The details about the general setting and the design of the injection utility are presented and the construction and installation of the ERT cables into the boreholes are explained in full. Preliminary measurements involving single-hole ERT measurements were obtained and processed with a 2D inversion algorithm to produce images of the subsurface. Results depict a very good correlation between ERT images and the lithology logs an indication of the reliability of the approach. This images offer inc...
Unidentified luminous phenomena have been observed in the low atmosphere over the Hessdalen valle... more Unidentified luminous phenomena have been observed in the low atmosphere over the Hessdalen valley for decades. First scientific investigation was done by E.Strand in 1984, where spiral movements of lights was recorded. The Science Camp program has conducted yearly field investigations since 2002 and has confirmed the existence of this spiral-behavior. (http://sciencecamp.no) Such behavior has also been documented in Alabama, USA. In September 2015 spiral like movement of lights was observed together with the more common spherical lights. This spiral movement indicates the presence of low atmospheric charged matter, moving in a magnetic field. A geological survey in 2014 reviled the presence of strong magnetic anomalies. The valley contains several abandoned copper mines containing Chalcopyrite and Magnetite. The Magnetite was not useful in the copper production, and left in heaps around the valley unused. This may contribute to the magnetic anomalies in the valley.
A two-phase geophysical survey is presented, whose aim was to investigate parts of the Ottoman Ha... more A two-phase geophysical survey is presented, whose aim was to investigate parts of the Ottoman Hamza Bey mosque located at Thessaloniki, Greece. Along with ground penetrating radar (GPR), which is a fully non-destructive method, a number of electrical resistivity tomographies (ERTs) were carried out. Bentonite mud electrodes were used instead of metal stakes, in order to comply with the non-destructive character of the whole operation. Our aim was to study the subsurface geological structures at the location of the mosque, and to detect and possibly map any ancient remains concealed under the monument. Both ERT and GPR results indicated a distinct, near surface horizontal discontinuity which was attributed to the presence of an ancient floor at the atrium area of the mosque. This floor was then revealed after a subsequent excavation. Moreover, high resistivity anomalies and distinct GPR signals were observed deeper at the atrium area. They are attributed to possible voids, remains o...
Journal of Applied Geophysics
25th European Meeting of Environmental and Engineering Geophysics, 2019
8th Congress of the Balkan Geophysical Society, 2015
In this work we present the results of the application of the electrical resistivity tomography (... more In this work we present the results of the application of the electrical resistivity tomography (ERT) technique into the mapping of the fissures that appeared in the Valtonera area (Amyntaion Munisipality, NW Greece).The results of ERT provide a satisfactory explanation to justify the expression of surface cracks in specific areas and this approach can be used to provide areas that are likely to be associated to fissures in the future.
Archaeologia Polona, 2015
The Bronze Age settlement of Akrotiri on the Greek island of Santorini/Thera was covered by thick... more The Bronze Age settlement of Akrotiri on the Greek island of Santorini/Thera was covered by thick layers of volcanic pumice during the massive eruption of the Thera volcano in approximately 1613 BC. Archaeological excavations conducted since 1967 have revealed the archaeological remains of an affluent prehistoric society, living in up to three-storey-high buildings that were richly decorated with vivid frescoes and furnished with sophisticated sewer systems. To date, three buildings have been excavated completely and approximately seven buildings have been partly uncovered in an area measuring some 90 m by 120 m (Doumas 1983). Archaeological excavation at Akrotiri inevitably exposes the archaeological remains and often fragile prehistoric architecture to the risk of destruction in case of stronger seismic events, which are very likely to occur at some point in the future, since the site is located in one of the world's seismically most active regions (Chouliaras et al. 2012), being located on an active volcano. Additionally, gradual decay caused, for example, by mud wasps and accidental damage threatens with the collapse of exposed architecture at this unique site. While it is impossible to prevent partial or total destruction of the excavated architecture in case of a larger earthquake, and while the long-term preservation of this cultural heritage is an extremely difficult challenge, it is possible to document the site digitally in three dimensions and in great detail. In 2013 and 2014, the LBI ArchPro documented the excavated areas in very high resolution, using laser scanning and latest photogrammetric methods. Within this project, which has been supported by the Conservation Trust of the National Geographic Society, additional geophysical archaeological prospection techniques have been tested in the vicinity of the archaeological site of Akrotiri in order to evaluate their potential to map still buried archaeological remains without exposing them to the risk of destruction. With exception of the location Kokkino Vouno (Red Mountain) west of the archaeological site, all other nearby areas are covered by more or less thick layers of volcanic ash and pumice, rendering the application of standard near surface geophysical archaeological prospection approaches challenging. The volcanic geology and the mostly large distance between the surface and the target structures renders the use of the otherwise commonly used magnetic prospection method less than promising. Early magnetic measurements were conducted in the area by Dr. Elizabeth Ralph from the university of Pennsylvania Museum in 1967 using a caesium magnetometer, still prior to the substantial archaeological discoveries made by Spyridon Marinatos (Mavor 1969).
Proceedings, 2016
Infiltration of rainwater is of major importance for old waste disposal sites where production of... more Infiltration of rainwater is of major importance for old waste disposal sites where production of leakage is taking place even after reclamation. In this work we present an ERT monitoring case study in a reclaimed Derveni Landfill. Previous studies in the area showed that important amount of water flows within the waste volume or by lateral groundwater flow or by direct infiltration of rainwater. Maag permeability measurements showed differential behavior of the top soil. Thus, geophysical monitoring of resistivity changes during injection of known conductivity water in high resolution 2D and 3D tomographies has been applied in two selected sites according permeability distribution map. 4D inversion of 2D and 3D data sets showed the flow paths of the injected salty water within the top soil up to the depth of almost one meter. At the same time increase of the resistivity has been observed deeper than one meter that cannot be easily explained. A possible explanation, except the case of disturbed current flow which could lead to artefacts, could be the biogas flow that is interrupted by the water cap of the injection. Both explanation are to be examined as a next step to the integration of the geoelectrical monitoring.
2017 9th International Workshop on Advanced Ground Penetrating Radar (IWAGPR)
In this work we study part of the Northern wall structure of the Heptapyrgion fortress of Thessal... more In this work we study part of the Northern wall structure of the Heptapyrgion fortress of Thessaloniki (UNESCO monument) that was identified to face moisture and structural problems. Moisture damage is a critical issue in the preservation and integrity of historic walls, thus it is necessary to detect it and to develop restoration plans. Heptapyrgion is one of the most important monuments in Thessaloniki so it is very crucial to use non-destructive techniques. To achieve that, a pilot GPR survey was conducted. The data obtained with 250 and 500MHz antennas were processed and interpreted in relation to the existing problem. To further assist the interpretation 2D GPR model simulations were carried out. GPR data was also compared to geoelectrical ERT data obtained at the same section on the wall. Overall GPR images are in good agreement with existing information and proved very useful in accessing the wall structure.
Abstract: The use of two geophysical methods in the investigation of the geological setting in th... more Abstract: The use of two geophysical methods in the investigation of the geological setting in the area of a dam foundation is presented in this study. The seismic method was used in order to map the structure of the upper layers near the riverbed. VES and resistivity tomographs were also carried out. The depth to the basement was estimated by interpreting the VES curves. Interpretation of the topographic images, along with the inferred models from the seismic data, revealed the thickness of the colluvial deposits.
ArchéoSciences
– Resistance and magnetic mapping, ERTs and aerial photography put together. – Fusion was attempt... more – Resistance and magnetic mapping, ERTs and aerial photography put together. – Fusion was attempted through curvelet transform. – The useful information of all methods is given in a combined image at the site of Philippi in Greece.
Bulletin of the Geological Society of Greece
This work describes the installation and preliminary measurements of an electrical resistivity to... more This work describes the installation and preliminary measurements of an electrical resistivity tomography (ERT) system to monitor the injection of recycled water into a confined aquifer in the area of Sindos. The aim is to provide, through time-lapse electrical resistivity tomography (ERT) measurements and processing, geoelectrical images of rather increased volumetric sampling around and between the holes and to obtain improved understanding of the flow and transport of the injected water. The details about the general setting and the design of the injection utility are presented and the construction and installation of the ERT cables into the boreholes are explained in full. Preliminary measurements involving single-hole ERT measurements were obtained and processed with a 2D inversion algorithm to produce images of the subsurface. Results depict a very good correlation between ERT images and the lithology logs an indication of the reliability of the approach. This images offer inc...
Unidentified luminous phenomena have been observed in the low atmosphere over the Hessdalen valle... more Unidentified luminous phenomena have been observed in the low atmosphere over the Hessdalen valley for decades. First scientific investigation was done by E.Strand in 1984, where spiral movements of lights was recorded. The Science Camp program has conducted yearly field investigations since 2002 and has confirmed the existence of this spiral-behavior. (http://sciencecamp.no) Such behavior has also been documented in Alabama, USA. In September 2015 spiral like movement of lights was observed together with the more common spherical lights. This spiral movement indicates the presence of low atmospheric charged matter, moving in a magnetic field. A geological survey in 2014 reviled the presence of strong magnetic anomalies. The valley contains several abandoned copper mines containing Chalcopyrite and Magnetite. The Magnetite was not useful in the copper production, and left in heaps around the valley unused. This may contribute to the magnetic anomalies in the valley.
A two-phase geophysical survey is presented, whose aim was to investigate parts of the Ottoman Ha... more A two-phase geophysical survey is presented, whose aim was to investigate parts of the Ottoman Hamza Bey mosque located at Thessaloniki, Greece. Along with ground penetrating radar (GPR), which is a fully non-destructive method, a number of electrical resistivity tomographies (ERTs) were carried out. Bentonite mud electrodes were used instead of metal stakes, in order to comply with the non-destructive character of the whole operation. Our aim was to study the subsurface geological structures at the location of the mosque, and to detect and possibly map any ancient remains concealed under the monument. Both ERT and GPR results indicated a distinct, near surface horizontal discontinuity which was attributed to the presence of an ancient floor at the atrium area of the mosque. This floor was then revealed after a subsequent excavation. Moreover, high resistivity anomalies and distinct GPR signals were observed deeper at the atrium area. They are attributed to possible voids, remains o...
Journal of Applied Geophysics