John D. Alexopoulos

• Ph.D
• Professor at National and Kapodistrian University of Athens

The present paper deals with an inhabited, creeping-mountainous landmass with profound surface deformation that affects the local community. The scope of the paper is to gather surficial and subsurface information in order to understand the parameters of this creeping mass, which is usually affected by several parameters, such as its geometry, subs...

The present study investigates the formation and development of a coastal barrier associated with the recent evolution of the beach/dune system of the Kyparissiakos Gulf (SE Ionian Sea, central Mediterranean Sea) during the late phase of the Holocene (Flandrian) transgression. The study is based on the application of combined geophysical (ERT: Elec...

The main purpose of this study is the subsurface investigation of two complex geological environments focusing on the improvement of data acquisition and processing parameters regarding electric and seismic tomographic techniques. Two different study areas, in central–east Peloponnese and SE Attica, were selected, where detailed geological mapping...

In this paper, we present a systematic GIS-based approach for producing updated, upscaled, unified and reevaluated maps for the Ionian Islands of Greece, which is an area of great geological interest. In particular, Cephalonia and Lefkada are two islands with an increased and intense seismicity. Therefore, a common GIS geodatabase was produced for...

The coastal environment of the west and south coast of Peloponnesus, Greece is characterized as an essentially tideless coastal environment exposed to high wave activity. Regarding the identification, the thickness and characteristics of the uppermost substratum of the selected coastal zones, at Hellonitis, Kyparissiakos and Messiniakos Gulfs, a de...

The tool assesses natural factors and the impact of human activities as well as the available mitigation measures in a cost-benefit perspective and with a view to mitigating the impacts of climate change. Therefore, the tool is designed to respond to both erosion (as a natural disaster) and erosion due to human (inappropriate) intervention, as well...

Greece is a country structured by land, several islands and sea. A regional gravity model of such a country demands the involvement of several types of gravity data in order to cover all its territory. In this paper, we present the development of a regional combined gravity model of Greece and its surrounding area, by integrating terrestrial, marin...

The Athenet network is the network of the Seismological Laboratory of the National and Kapodistrian University of Athens. We present the geophysical investigation that has been carried out at six seismological stations of the Athenet network for their site characterization. More specifically, at the location of each seismological station, four geop...

This paper presents the methodology of an applied geophysical and remote sensing research at river deltas for their subsurface and surface structure and its application in the deltaic plain of Pineios River (Thessaly, Greece). The scope is to primarily calculate the thickness of deltaic post alpine deposits, with the contribution of Transient Elect...

The study area of Rodafnidia on the island of Lesbos (Greece) is considered of archaeological interest, as Paleolithic stone tools have been recovered through excavation and collected from the ground surface in recent years. Geologically, the area is mostly covered by Quaternary post-alpine deposits and volcanic rocks. This paper presents the appli...

Lefkada and Corfu old towns are located in the western part of Greece, in the Ionian Sea. Their proximity to the Hellenic subduction zone (HSZ) is the reason for their intense seismicity. The main goal of this study was the estimation of the geotechnical characteristics of the subsurface, with the contribution of applied geophysical techniques. The...

Seismic velocity and density calculations for the estimation of the elastic moduli of the Athens schist formation.

Determination of the physical parameters of lateritic bauxite formation with the contribution of geophysical methods. In this paper we present the results of a near-surface geophysical survey carried out for the investigation of geotechnical engineering characteristics in selected locations of the seismological stations of the National Network, Sec...

Seismicity accompanied with intense ground deformation in the Ionian Sea (W. Greece) is mainly generated along the Cephalonia-Lefkada Transform Fault Zone (CLTFZ), in the central Ionian, and on the northwestern termination of the Hellenic subduction margin in the south. Pre- co- and post-seismic ground deformation analysis is performed at the broad...

Investigation of the subsurface structure of Lefkada town using a multidisciplinary geophysical approach. In this paper we present the preliminary results of a near-surface geophysical research carried out on Lefkada island, for the investigation of the geological setting of Lefkada town. The geophysical survey has also been extended in selected lo...

The project ILIDA-KIT is based on multiple levels of information organized in a multi-disciplinary interactive GIS platform, which lead to the development of a set of appropriate indicators (e.g., environmental, geographical, economic). The ultimate purpose of the Tool is in the selection of the most appropriate anthropogenic intervention; the latt...

The current study aims to clarify the structural regime of the deltaic valley of Pineios river (Thessaly, Greece). The structural control of a deltaic area is usually a crucial parameter for its Palaio-geographical evolution and the latter needs to be clear for the contemporary conservation of such a sensitive ecotope environmentally. The investiga...

Featured Application Field validation of combined remote sensing and seismological data after a large earthquake. Abstract The Arkalochori village in central Crete was hit by a large earthquake (Mw = 6.0) on 27 September 2021, causing casualties, injuries, and severe damage to the infrastructure. Due to the absence of apparent surface rupture and...

We investigate an earthquake sequence involving an Mw = 4.6 mainshock on 2 December 2020, followed by a seismic swarm in July–October 2021 near Thiva, Central Greece, to identify the activated structures and understand its triggering mechanisms. For this purpose, we employ double-difference relocation to construct a high-resolution earthquake catal...

Seismicity in the Ionian Sea (W. Greece) is mainly generated along the Cephalonia–Lefkada Transform Fault Zone (CLTFZ) in the central Ionian, and on the northwestern termination of the Hellenic subduction margin in the south. Joint pre-, co- and post-seismic ground deformation and seismological analysis is performed at the broad Ionian area, aiming...

Coastal areas constitute a very dynamic environment, balancing between numerous natural and anthropogenic processes liable to sometimes hazardous geomorphic phenomena. Especially in tectonically active coastal regions and areas of high economic value, slope failures can have significant impacts and therefore need careful and detailed examination. T...

Based on the results of a previous terrestrial gravity survey that was carried out in Athens basin (Greece) some indications of correlation between terrestrial gravity data and isoseismal maps of Athens earthquake (7/9/1999) had been revealed. In this paper, we will present a research for the same area based on a new approach, which investigates th...

1960 αλλάζοντας έτσι την μορφή και την ρυμοτομία της περιοχής. Βασικός στόχος της παρούσας εργασίας είναι η διερεύνηση των μέτρων βελτίωσης καθώς και των προοπτικών ανάπτυξης της μαρίνας Γλυφάδας που αποτελείται από 4 λεκάνες όντας μία από τις πιο όμορφες και εξελιγμένες μαρίνες της χώρας αφού αποτελεί σημαντικό πόλο έλξης τουριστικών σκαφών. Για τ...

An urban gravity survey with more than 1120 measurements was carried out in order to adumbrate the deeper subsurface of Athens city basin. The aim was to gather quantitative information of the subsurface structure derived from the acquisition of gravity measurements. At first, a gravity base network has been established for the data collection. The...

Relevance. In this paper the feeding mechanism of springs distributed around the broader area of Delfini at NE side of Chios Island is explored, in an effort to locate possible fresh water paths inland before they are discharged to the sea. The drilling of hydro wells for more production is of vital importance to cover the drinking and irrigation n...

The gravity method has been applied, with a total of 1.122 gravity measurements for the subsurface investigation of the geotectonic structure beneath the urban and sub-urban areas of Athens basin. The aim was to gather new information for the subsurface geological and tectonic structure of Athens basin and re-assess the seismic hazard risk of the a...

The current study aims to clarify the hydrogeological regime of the deltaic valley of Pinios river (Thessaly, Greece). Its purpose is to map the existing aquifers below the deltaic plain, but also to assess the quality of their water (detect possible seawater intrusion), through the combined application of VES and TEM soundings. The results of the...

A disastrous earthquake of the past (7th September 1999) was the reason for acquiring 1.122 urban gravity measurements in order to investigate and model the deeper subsurface of Athens city basin. The aim was to gather any additional quantitative subsurface information based on the gravity survey, such as the density distribution provided by the 3D...

The excavation trenches by the Department of History and Archaeology of the NKUA at the archaeological site of Plasi Marathon (Attica, Greece) have already revealed several architectural remains of the Classical period. A combined GPR and ERT survey was initiated in order to determine the existence and geometry of additional buried structures in th...

The disastrous phenomenon of aseismic ground fissures along the eastern Thessaly basin has deteriorated since 1989. The main reason for these fissures is the over-pumping, which leads to differential vertical compaction of the aquifer system and subsidence on the land surface. In this paper, we present the results of a combined geophysical survey a...

Mediterranean Temporary Ponds (MTPs) constitute priority habitat under the European Union Habitats’ Directive. They are inhabited by rare species and subjected to unstable environmental conditions. Lakes and ponds act as early indicators of climate change, to which high altitude ecosystems are especially vulnerable. This study presents a full datas...

The gravity method has been applied, with a total of 1.122 gravity measurements for the subsurface investigation of the geotectonic structure beneath the urban and sub-urban areas of Athens basin. The aim was to either verify previously mapped concealed fault zones or even discover new concealed faults that may affect the city in the future by gene...

Coastal zone monitoring is essential in order to understand their evolution and incorporate sustainable coastal management practices. Frequent data collection is essential but often surveys can be costly and time-consuming. Several costly and time-consuming tools and techniques have been developed during the last few years for change detection and...

In gravity surveys, many unwanted effects are produced by geological or non-geological sources. These calculable effects have to be removed through the data reduction procedure. Common corrections in gravity measurements are those for the instrument drift, the tide, the Free Air, the Bouguer and the terrain effect. However, when we deal with gravit...

River deltas sustain important ecosystems with rich biodiversity and large biomass, as well as human populations via the availability of water and food sources. Anthropogenic activities, such as urbanization, tourism and agriculture, may pose threats to river deltas. The knowledge of the factors controlling the regional water quality regime in thes...

In this paper we discuss the preliminary results of the Transient Electromagnetic Method (TEM) that was applied in the area of Karla Lake, located in the East Thessaly basin. A grid of 71 TEM soundings was planned and executed in order to investigate the subsurface lithological and hydrogeological conditions of the area. The geological regime of th...

Climate change is expected to affect the hydrological cycle, altering seawater level and groundwater recharge to coastal aquifers with various other associated impacts on natural ecosystems and human activities. As the sustainable use of groundwater resources is a great challenge for many countries in the world, groundwater modeling has become a ve...

The present paper presents measurements of water flow and suspended particulate material of Pinios River (Thessaly) during the hydrological year 2013/2014. The measurements were carried out in two positions before Pinios enters the agricultural deltaic plain and one inside the delta. Furthermore, an effort is made to estimate the water contribution...

In tectonically active areas, such as in the northwest Peloponnese of western Greece, geomorphic processes are strongly influenced by active faulting; in many cases such faults cannot be easily identified. In this paper we apply multidisciplinary analysis (morphotectonic indices, neotectonic mapping, geophysical surveys and remote sensing technique...

Στην ευρύτερη περιοχή του Δελταϊκού πεδίου του Πηνειού ποταμού, στη Θεσσαλία και στα πλαίσια εφαρμοσμένη γεωπεριβαλλοντικής έρευνας, αναπτύχθηκε προκαταρκτική γεωφυσική έρευνα. Στην κατεύθυνση αυτή καταβλήθηκε προσπάθεια να αναπτυχθεί ένας κάναβος θέσεων-μετρήσεων ικανός να καλύψει το σύνολο του πεδίου, έτσι ώστε να αναδειχθεί μια γνώση που θα συμβ...

This study aims at defining the groundwater flow regime and the principal hydro-geochemical processes controlling groundwater quality in the deltaic plain of River Pinios (Thessaly-Greece) and investigating whether seawater intrusion and pollution are influencing groundwater quality. Groundwater level monitoring from October 2012 to September 2013...

In this project the geological subsurface structure of the delta of the river Pinios is investigated through the contribution of geophysical soundings. In order to investigate the lithologic structure of the entire deltaic field, geophysical soundings were performed with the geoelectrical method of vertical investigation of the resistivity distribu...

The present study aims to clarify the hydrogeological regime of the phreatic aquifer, primarily its spatial distribution, through a combined interpretation of the preliminary results of an extensive geophysical research conducted in the area and of the hydrogeological data collected in parallel scientific actions by previous researchers. In the con...

1:5.000, (β) ψηφιακή επεξεργασία πρόσφατης δορυφορικής εικόνας υψηλής χωρικής και φασματικής διακριτικότητας, (γ) μορφοτεκτονική ανάλυση, (δ) επιτόπιες υπαίθριες παρατηρήσεις και (ε) γεωφυσικές μετρήσεις. Οι ποτάμιες αποθέσεις και προσχώσεις καλύπτουν τη μεγαλύτερη έκταση της περιοχής, ενώ παράκτιοι σχηματισμοί εκτείνονται σε όλη την παραλιακή ζώνη...

A geophysical survey was performed at selected locations of Mt. Oiti and Mt. Kallidromon characterized by the hosting of priority habits of Mediterranean temporary ponds and the threatened plant species of Veronica oetaea, in order to understand the geoenvironment and contribute to the conservation of biodiversity. Primarily, the formation of these...

A geophysical research was carried out to investigate the lithostarigraphic substratum characteristics of the dune field of the central Kyparissiakos Gulf (W. Peloponnese, Greece), which is characterised by the presence of four dune lines. For this purpose, the geophysical techniques of Electrical Resistivity Tomography (ERT) and Vertical Electrica...

A geophysical survey was carried out in the archaeological site of Kyparissia (Megalopolis, Greece) applying the Very Low Frequency technique, as preliminary combined with highly detailed Electrical Resistivity Tomography. Settlements of the ancient city of Trapezous (limestone slabs 0.5m height x 0.5m width) have already been uncovered from the lo...

Η παρούσα Επιστημονική Έκθεση υλοποιήθηκε στο πλαίσιο της έρευνας με κωδικό ΕΛΚΕ/ΕΚΠΑ 70/3/12657 και τίτλο «Παροχή Υπηρεσιών Συμβούλου για την Συμπλήρωση της εγκεκριμένης Ε.Π.Μ. Θίνες και παραλιακό Δάσος Ζαχάρως, Λίμνη Καϊάφα, Στροφυλιά, Κακκόβατος και θαλάσσια περιοχή κόλπου Κυπαρισσίας». Η επιστημονική έκθεση κάλυψε την ευρύτερη παράκτια ζώνη του...

Extensive ground fissures frequently occur within the eastern Thessaly basin, in central Greece and have been since 1989. This paper aims to give a preliminary explanation for their generation reasons by interpreting the results of a dense geophysical survey along the basin. This is combined with drilling data, as well as field work tectonic measur...

The scope of the present contribution is to investigate the formation and evolution of the Kyparissiakos coastal dune field, during the last transgression (Holocene), on the basis of geophysical techniques (ERT, VES), detailed morphological mapping and existing geoenvironmental information.

A coastal management study at areas with steep anaglyph requires detailed knowledge of the onshore surface and subsurface regime regarding the erosional procedures. Active faults produce dynamic and continuously evolving geomorphological structures, which require investigation and continuous monitoring. Detailed mapping on and adjacent to these sur...

In this paper we present a combination of several near surface geophysicalΒ investigation techniques with high resolution remote sensingΒ image interpretations, in order to define the groundwater flow pathsΒ and whether they can be affected by future seismic events. A seasonalΒ spring (Amvrakia) located at the foot of Meteora pillars near the villa...

The scope of the research project is to investigate the consequences of climate change on deltaic plains, as one of the most vulnerable coastal and wealth-producing ecosystems. The Pinios river delta, located in the region of Thessaly (Greece) has been selected as a case study, as one of the largest Greek rivers with very limited flow controls. But...

The Amvrakia spring is located at the bottom of Meteora pillars and more specifically near the village of Kastraki (Kalambaka municipality). It is a seasonal spring since it functions only during the wet period. The Meteora conglomerates which dominate the area are characterized by large discontinuities creating a network of groundwater pathways ab...

During the last years the broader area of Koropi (Mesogheia-Greece), has faced rapidly increasing problems concerning irrigation and watering of the town, due to the brackish water in the water supply boreholes. Our main target is to determinate the subsurface geological structure of the study area, located NE of the Koropi city, where alterations...

During the last years the broader area of Koropi (Mesogheia-Greece), has faced rapidly increasing problems concerning irrigation and watering of the town, due to the brackish water in the water supply boreholes. Our main target is to determinate the subsurface geological structure of the study area, located NE of the Koropi city, where alterations...

The scope of the present contribution is to investigate the formation and evolution of the Ververonda 'lagoon' that belongs to the South Argolid peninsula (Porto Heli region) during the last transgression (Holocene) period. This is achieved by utilising existed information and the production of the appropriate supplementary data; the former refers...

In this paper the feeding mechanism of springs distributed around the broader area of Delfini at NE side of Chios island is explored, in an effort to locate possible fresh water paths inland before they are discharged at the sea. The drilling of more production hydro wells is of vital importance in order to cover the drinking and irrigation demands...