G.N. Tsokas

Aristotle University of Thessaloniki | AUTH · Laboratory of Physical Geography

The onshore Axios-Thermaikos basin in northern Greece is a sedimentary composite depocenter of 4km depth, that developed tectonically during the Cenozoic extending over the alpine basement of the Internal Hellenides. It consists of Lower Eocene to Quaternary sediments deposited unconformably over the Mesozoic emplaced ophiolite and sedimentary rock...

The publication at hand are the proceedings of the 15th International Conference on Archaeological Prospection held between March 28 and April 1, 2023, in Kiel, Germany. The content of the articles ranges from local to large-scale case studies all over the world and from various archaeological times, over methodological improvements, new processing...

The publication at hand are the proceedings of the 15th International Conference on Archaeological Prospection held between March 28 and April 1, 2023, in Kiel, Germany. The content of the articles ranges from local to large-scale case studies all over the world and from various archaeological times, over methodological improvements, new processing...

This work uses two, and three-dimensional Electrical Resistivity Tomographies (ERTs) applied on standing monuments to investigate moisture presence and possible moisture migration through time-lapse monitoring. The whole process was applied to one of the main pillars in Thessaloniki’s Rotunda (Central Macedonia, Greece). Two-dimensional ERTs appli...

The Kastrouli Late Bronze settlement in Phocis province, central Greece, has been proved to have been an important center in the periphery of the Mycenaean palaces. It was reused at least partially and was cultivated until the 20th century. The presence of a flat area off the Kastrouli hill and the seasonal flooding nowadays led to the present inve...

The contemporary trend of research projects and works are presented on selective issues of archaeometry, archaeology and Egyptology. The current status in research in the area of SE Mediterranean on cultural heritage and archaeological/historical reflections alone and/or coupled with archaeological sciences of eleven papers are placed within an upd...

A detailed gravity survey with 235 measurements was carried out at the King Fahd University of Petroleum and Minerals campus, which is located at the crest of the oil-bearing Dammam Dome (Eastern Province of Saudi Arabia). This survey allows us to better understand the geometry of the underlying Dammam Dome and its tectonic regime. The acquired dat...

The study area is a part of Dammam Dome that is situated at King Fahd University of Petroleum & Minerals (KFUPM) campus, Dhahran, Kingdom of Saudi Arabia. The gravity survey was conducted as a pilot case study to explore part of Dammam Dome in greater detail. Gravity data were collected solely during night hours due to low noise levels. A significa...

A large-scale geophysical survey was carried out at the foothills of a topographic table hosting the ruins of the ancient city ‘Trikorynthos’, in the area of Marathon, north of Athens. The explored site assumed to host remnants of ancient constructions belonging to the ancient city. Although the explored site is associated with the final phase of t...

Electrical Resistivity Tomography (ERT) is widely known for providing valuable information for numerous archaeological prospection problems in two and three dimensions. The purpose of this work was to detect possible moisture inside one of the main pillars of Thessaloniki’s Rotunda (Region of Macedonia, Greece), a Unesco heritage monument using var...

The onshore Thermaikos basin is the northwestern extension of the offshore Thermaikos basin, located at the area west of Thessaloniki, in northern Greece. It consists a sedimentary basin, where thick sediments dating from Paleogene to Quaternary are overlaying the older ophiolite and deep-sea Mesozoic formations of Axios geotectonic zone. Thermaiko...

In the last few years, the idea of combining images, called image fusion, appeared and it has become a critical area of research and development. Image fusion can be defined as the process of combining images, taken from the same scene and create one single image containing all the essential information of the original images. A single sensor is no...

The knowledge that archaeological prospection is shaped by modern attitudes and procedures is important to the future of archaeology. Although geophysical studies have been applied to archaeological and historical sites over time with intermittent success, it is possible to derive great effects when used appropriately. It is most significant when a...

The Aqueduct of Eupalinos was built in the mid-sixth century B.C, on the island of Samos that lies in the archipelago of the north Aegean Sea. Herodotus (481-425 B.C.) was the first historian to refer to the monument. He names Eupalinos, son of Naustrophus, born in the city of Megara as the engineer responsible for the design and construction of th...

The geophysical investigations aiming to image the interior of the huge tumulus of Kastas in Amphipolis in northern Greece commenced on November of 2014 and continued sporadically until the first months of 2017. The electrical resistivity tomography (ERT) method was exclusively employed in both conventional and innovative schemes. Due to the immens...

In this paper the application of flat base electrodes into a building's basement is examined. The aim of this study was to locate ancient walls possibly situated underneath a building, lying on Ag. Dimitriou road in Thessaloniki (Greece). During ERT surveying, an archaeological excavation took place on the roadway outside the building. The excavati...

Non-destructive investigation of monuments can be an extremely valuable tool to evaluate potential structural defects and assist in developing any restoration plans. In this work, both Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) techniques were applied to a tower wall of the Heptapyrgion fortress located in Thessaloni...

The interconnection between cultural heritage found in terrestrial and marine environments is beginning to garner international more scholarly attention as researchers investigate the linkages between human adaptation to changing coastal environments. In terms of world cultural heritage, land and sea should be considered as an integrated system. As...

The availability of overlapping geophysical data produced by different sensors provides complementary information about the investigation area. However, joint interpretation of these geophysical images is challenging. One common problem is the registration of the images that is necessary to compare features appearing in dissimilar datasets. Measure...

The paper describes the conduct and results of geophysical prospecting in the mountainous area of ancient Helike in Achaea. Several linear and in cases rectangular anomalies were detected, which may represent buried ancient ruins in this location.

The article describes the conduct and results of geophysical prospecting in the mountainous area of ancient Helike in Achaea. Several linear and in cases also rectangular anomalies were detected, which may represent buried ancient ruins.

The applicability of surface-to-tunnel electrical resistance tomography (ERT) measurements using a simulation tank for imaging subsurface targets is studied in this work. The tank was filled with water and inside of it was placed firmly a plastic construction where all targets were placed. Some of the targets that used were: a void plastic cylinder...

In this work we propose an algorithm for producing adaptive optimized geoelectrical protocols related to the time lapse monitoring. The optimization method is based on the direct use of the Jacobian matrix as a metric for selecting the optimized data sets. The algorithm was developed into the Matlab environment and was tested with synthetic data. T...

The main objective of this study is the determination of the Moho discontinuity in the Hellenic area based on gravity data inversion. High-resolution (2 arcmin) and accuracy (±2 to ±3 mGal) gravity data were used in the computations following the Parker–Oldenburg iterative method, and a low-pass filter was applied to gravity information towards the...

The 2.5‐km‐long Eupalinian Aqueduct in the island of Samos, Greece, comprises the most impressive sample of ancient Greek engineering surviving almost intact. The main construction is a tunnel 1036 m long and almost 1.8 m wide excavated from both ends into mainly the massif limestone. In some parts of the overall length of about 240 m, the tunnel i...

The geophysical techniques are used for investigating the interior of tumuli in order to locate burial monuments covered by the embankment. This is a contribution towards saving the integrity of the construction since the tumuli by themselves comprise monuments which must be preserved. The electrical resistivity tomography (ERT) comprises a fully n...

In the present work we examine the crustal structure in the wider Adriatic Sea region using a newly presented Bouguer database derived from the integration of satellite, marine and inland gravity measurements. The observed large-wavelength Bouguer anomalies clearly correlate with the deeper crustal - upper mantle structural features, revealing new...

New geoinformatic technologies have recently had a transformative effect on landscape archaeology, particularly by facilitating the high resolution acquisition and analysis of data over large areas. These techniques have fundamentally changed the nature and scope of questions that can be addressed regarding the archaeological record. Despite this s...

Magnetization differences in rocks are related with differences in the content of magnetic minerals within rock units. Assuming that magnetic properties (susceptibility and/or remanence magnetization) are discernible between the various rock units, magnetic field anomalies could provide valuable information for the texture of lithological units and...

The surviving Tunnel of Eupalinus comprises one of the greatest engineering achievements of ancient Greeks. The tunnel itself (1036 m long) was carved in the sixth century bc through solid rock by digging from both ends and advancing to the central meeting position. The method for achieving the meeting of the two simultaneously advancing branches i...

In this article we provide a preliminary report of the work carried out between 2010 and 2012 as part of the Makrakomi Archaeological Landscapes Project (MALP). The programme of research is carried out in co-operation between the Swedish Institute at Athens and the 14th Ephorate of Prehistoric and Classical Antiquities at Lamia. The interdisciplina...

Airborne magnetic surveys provide a cost effective, quick and accurate way to map the subsurface distribution of magnetization for large, usually inaccessible, areas. Differences in magnetization of rock units are related with differences in the content of magnetic minerals within rock units (i.e. their magnetic susceptibility) and their remanent m...

Management of waste disposal is a major issue that authorities had and still have to deal with. The construction of landfills used to be the main way to manage the great volume of waste. At the present time, the construction of sanitary landfills is the dominant option in Greece, while old waste disposal sites where no protection standards had been...

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 me...

The purpose of this paper is the development of a new Bouguer anomaly map for the broader Adriatic Sea area to be used as geo-scientific tool which will answer questions mainly regarding the deep and intermediate depth structure of the Adriatic and its surrounding areas. As a first step, a consistent, high-resolution and accuracy free-air gravity a...

Artificial erected hills like tumuli, mounds, barrows and kurgans comprise monuments of the past human activity and offer opportunities to reconstruct habitation models regarding the life and customs during their building period. These structures also host features of archaeological significance like architectural relics, graves or chamber tombs. T...

In this work various image fusion techniques are used between one satellite (Quickbird) and one geophysical (electric resistivity) image to create various combinations with higher information content than the two original images independently. The resultant images provide more information about possible buried archaeological relics. The examined ar...

Various geophysical methods were used to explore the subsurface of the prehistoric site of Mitrou. Geophysical research was essential for selecting significant areas for excavation as well as for guiding archaeological fieldwork and complementing its results. Resistivity mapping and differential magnetometry detected patterns of well-structured ano...

Geophysical field measurements are subject to errors, which consequently comprise part of the data and subsequently they are propagated through processing techniques. Some of these errors can be controlled and eliminated, but others such as the errors introduced by the measuring instrument cannot be avoided. Moreover, the field data are collected a...

Various edge delineating methods (edge mappers) are tested on different types of synthetic data produced by calculating the response of a model of buried ancient ruins. The model was constructed to resemble a commonly occurring situation with ruins of two historical phases buried one beneath the other. These weak signals of relatively small wavelen...

This work describes the application of the electrical resistivity tomography (ERT) technique, in both surface and cross-hole modes, for subsurface exploration in an urban environment. The objective was to image the foundations of the Thessaloniki city walls (Region of Macedonia, North Greece) at locations that will be affected by the construction o...

This paper presents results from different fusion techniques between geophysical images from different modalities in order to combine them into one image with higher information content than the two original images independently. The resultant image will be useful for the detection and mapping of buried archaeological relics. The examined archaeolo...

The ancient city of Europos (or Evropos), is located in Central Macedonia (northern Greece), not far from the city of Thessaloniki. The purpose of this research project, is to detect and delineate buried potential archaeological remains, and propose them to archaeologists for further field work. QuickBird, IKONOS, SPOT and ALOS satellite imagery ha...

This paper presents an effective registration method between two geophysical images from different modalities, namely magnetic and electrical, in order to increase the information obtained from the two original images independently. In order to achieve the registration, random local transformations were applied in 55 5 randomly chosen windows of th...

We present the application and results of a fully non-destructive electrical resistivity tomography (ERT) survey conducted at the Acropolis of Athens. The aim of the survey to investigate the space behind the south wall of the Acropolis. The electrode lines were deployed vertically and horizontally on the wall as well as on the top of the hill. Fur...

In this work a new algorithm for the fast and efficient 3D inversion of conventional 2D surface electrical resistivity tomography lines is presented. The proposed approach lies on the assumption that for every surface measurement there is a large number of 3D parameters with very small absolute Jacobian matrix values, which can be excluded in advan...

The Strymon basin is one of the most important sedimentary basins in Northern Greece where significant geothermal fields are located. The SW part of the Strymon basin manifests geothermal interest. Available geophysical data (seismic, gravity, magnetic and electrical data) contributed to the identification of major faults that control the fluid-flo...

Complex attributes of the magnetic signal are computed using a multiple source approach. Polygonal bodies are considered and the attributes of each corner are summed to produce the overall response; that is a decomposition of the polygonal body into magnetized steps to simulate the vertices. The method is tested on synthetic examples of buried ditc...

Tumuli are artificially erected small hills that cover monumental tombs or graves. In this work, the surface three-dimensional (3D) Electrical Resistivity Tomography (ERT) method, composed of dense parallel two-dimensional (2D) tomographies, was used to investigate the properties of the tumuli filling material and to resolve buried archaeological s...

Two stations were installed in the Southeastern Thessaly basin (Central Greece), recording the geomagnetic and telluric fields from 1993 to 1996. The aim was to detect long-term abnormal changes of the telluric field, which were possibly related to imbedding earthquakes. Between January 1993 and October 1996, 213 and185 (Neraida and Mavrolofos stat...

Many attempts have been made to disclose anomalous changes of the electromagnetic field in relation with tectonic earthquakes. We tentatively develop a new approach based on the energy and polarity of the electric field, and apply this method to the seismicity in Greece. The study of the parameters of the horizontal electric field is realized in a...

Introduction The direct current resistivity method is nowadays a well established geophysical technique, used routinely and successfully in the detection and mapping of concealed subsurface structures, like walls, ditches and anthropogenic or natural cavities (Dahlin and Zhou, 2004). In archaeological geophysics, tombs constitute the most common su...

Electrical resistivity is a well established and widely used prospection method. The technique has also become a valu- able and inseparable tool in archaeological site evaluation and excavation planning (Clark, 1990). Nowadays, it is routinely used in mapping the sub-surface resistivity varia- tion of an archaeological site. The compilation of maps...

Introduction A survey involving both surface and cross borehole Electrical Resistivity Tomographies (ERTs) is described. It was conducted at various parts of the western wall of the city of Thessaloniki (N. Greece) aiming to estimate the extent of the walls’ foundations. The Thessaloniki city walls have been initially erected during the Hellinistic...

Geophysical investigations through mobile multi-electrode systems, such as the automatic resistivity profiling (ARP) method, can increase the size of the surveyed areas without jeopardizing the spatial resolution of the survey. The representation of the apparent resistivity data in maps corresponding to the different measuring dipoles is sufficient...

In his journey through Achaea in the second century AD, Pausanias mentioned the destroyed Classical site of Helike on the sea and noted that its ruins were still visible underwater near the southwest shore of the Corinthian Gulf. In 2001, the Helike Project excavators discovered on the coastal plain of Helike southeast of Aigion the first ruins of...

In this work a strategy for optimizing ERT data sets based on the sensitivity matrix is examined and compared with the existing optimization schemes as well as with the most commonly used traditional arrays. Synthetic data tests illustrate that existing ERT data optimization approaches are highly dependent on the subsurface resistivity. As a result...

The need for information about the depth extend of the buried targets was one of the main reasons for the development of the electrical resistivity tomography (ERT). The term implies that automated multiplexers are used for data acquisition which are subsequently inverted by some mathematical scheme. The present work presents the merits of resistan...

The magnetic difference, the quantity measured by magnetic gradiometers, is considered to be the convolution between a function that controls the anomaly pattern and another that controls the strength signal. These are called shape and amplitude functions, respectively. They are distinct and analytically determined; thus, after the assessment of a...

The area inside and around the church of Kapnikarea in Athens (Greece), was explored by means of electrical resistivity tomography (ERT). ‘Flat base’ electrodes were used exclusively because the survey had to be fully non-destructive. The performance of ‘flat base’ electrodes was satisfactory, leading to inversions of small root mean square (RMS) e...

The optimum processing technique (2D vs. 3D inversion) to interpret and visualize parallel and/or orthogonal two-dimensional surface Electrical Resistivity Tomography data collected from archaeological sites is examined in this work. A simple modification of a standard resistance-meter geophysical instrument was implemented in order to collect para...