Now showing 1 - 5 of 5
  • Publication
    Geophysical investigation for the detection of liquefaction phenomena in an archaeological site, Lechaion, Greece
    (Society of Exploration Geophysicists, 2015) ;
    Apostolopoulos, G.
    ;
    Minos-Minopoulos, D.
    The area of Lechaion located in the northeastern part of the Peloponnese (Greece) is of great archaeological interest because it represents the western harbor of ancient Corinth and includes the remains of an early Christian basilica destroyed during a series of earthquakes in the sixth century AD. Numerous depressions and buckling structures of circular and linear geometry observed on the decorated floor of the basilica are indicative of ground deformation processes possibly related to earthquake-induced ground liquefaction. Electromagnetic (with a conductivity meter), ground penetrating radar (GPR) (with 250 MHz shielded antenna), and electric (ERT) methods have been applied in an effort to study the properties of the substratum and to identify indicative features related to ground liquefaction phenomena. The electromagnetic survey that was used as a reconnaissance method with both coil orientations provided valuable information through data processing, identifying zones of higher conductivity that favor liquefaction, or even the detection of the features themselves. The GPR method detected vertical zones that could represent sand vents either directly with multiple diffractions or indirectly through severe wave attenuation and reduction of the anomaly intensity due to finer sand and increased water saturation. Finally, the ERT method detected layering and the geologic status of the survey area but more importantly, it successfully detected narrow vertical zones of lower resistivity at shallow depths corresponding to sand vents via distinct variations in grain size and permeability. This combination of geophysical methods has successfully detected the dominant trend of east-northeastern-west-southwestern direction and a minor vertical one of north-northwestern-south-southeastern direction of surface depressions caused by liquefaction and generally can successfully provide valuable information on the extent and characteristics of ground liquefaction features in areas of geotechnical or archaeological interest located in regions of intense seismic activity. © 2015 Society of Exploration Geophysicists.
    Scopus© Citations 8  112
  • Publication
    Liquefaction features at an archaeological site: Investigations of past earthquake events at the Early Christian Basilica, Ancient Lechaion Harbour, Corinth, Greece
    (Elsevier, 2015) ;
    Minos-Minopoulos, D.
    ;
    Apostolopoulos, G.
    ;
    Lekkas, E.
    ;
    Dominey-Howes, D.
    A synthesis of investigations carried out at the archaeological site of the Early Christian Basilica, located in the ancient harbour of Lechaion, Corinth, Greece in order to study the origin and triggering mechanism of deformation structures observed on the temple floor, is presented. These surface structures are indicative of earthquake induced ground liquefaction and their relationship with the subsurface soil stratigraphy and structure is examined. Investigations of stratigraphic data from archaeological excavations conducted from 1956 to 1965 provide indications of artificial fill deposits overlying a sandy-gravelly substratum. Geophysical survey of EM, GPR and ERT provided further information regarding the substratum properties/stratigraphy of the site indicating subsurface fissures and lateral spreading trends that are in agreement with the surface deformation structures. Lithostratigraphic data obtained from four vibracores drilled in the southern aisle of the temple, suggest estuarine deposits of coarse sand to fine gravel with grain size properties indicative of layers with high liquefaction potential. The results of the study, suggest at least three seismic events that induced ground liquefaction at the site. The first event pre-dates the construction of the Basilica, when Lechaion harbour was in operation. The second event post-dates the construction of the Basilica potentially corresponding to the regionally damaging A.D. 524 earthquake, followed by the third event, that commensurate with the A.D. 551 earthquake and the destruction of the temple. © 2015 Elsevier B.V.
    Scopus© Citations 8  48
  • Publication
    Prediction of Soil Loss in a Reservoir Watershed Using an Erosion Model and Modern Technological Tools: A Case Study of Marathon Lake, Attica in Greece
    (2020) ;
    Kapsimalis, V.
    ;
    Evelpidou, Niki
    ;
    Apostolopoulos, G.
    ;
    Xanthakis, M
    ;
    Xanthopoulos, G
    ;
    Panagiotis, S
    Marathon Lake is an artificial reservoir with great environmental, ecological, social, and economic significance because it was the main source of water for Athens, the capital of Greece, for many years. The present study details the first attempt to map sedimentation in Marathon Lake in detail, using bathymetric mapping and soil erosion field surveying of the torrent watershed areas. First, the results of a bathymetric survey carried out in 2011 were compared with topographic maps that pre-date the construction of the dam. Based on this comparison, an estimated 8.34 hm3 of sediment have been deposited in the 80 years since the dam’s construction. In the current survey, the Revised Universal Soil Loss Equation (RUSLE) was used to estimate soil loss in the watershed area of the streams that end in Marathon Lake. The estimated value from the RUSLE was substantially lower (3.02 hm3) than that calculated in the bathymetric survey.
      96  56
  • Publication
    Reconnaissance geophysical survey for the detection of salinization and stratigraphy in Thorikos Valley, Attica, Greece
    (European Association of Geoscientists and Engineers, EAGE, 2014) ;
    Apostolopoulos, G.
    ;
    Kallioras, A.
    ;
    Stathopoulou, K.
    ;
    Vlassopoulou, A.
    A reconnaissance geophysical survey is a starting task of a multitasking collaboration to detect all hydrogeological (extent of salinization), stratigraphical, geological features of Thoriko valley in order to reconstruct the environment in ancient times as well as to interpret the position of the various archaeological monuments existing in the area. Electromagnetic measurements with conductivity meter, made in a quick mode with a cart dragged by car, have given, after data evaluation and filtering, valuable information regarding near surface salinization phenomenon. In addition ERT and IP profiles give deeper detection of this phenomenon discriminating media of various clayey content.
      44
  • Publication
    Was the Piraeus peninsula (Greece) a rocky island? Detection of pre-Holocene rocky relief with borehole data and resistivity tomography analysis
    (Academic Press, 2014) ; ;
    Apostolopoulos, G.
    ;
    Goiran, J.-P.
    According to historical documents, Piraeus was a rocky island consisting of the steep hill of Munichia, known as modern-day Kastella. It was connected to the mainland by a low-lying stretch of land ("Halipedon") that would flood with sea water most of the year and was used as a salt field whenever it dried up. Apart from being an area of archaeological interest, the extended area of "Halipedon" is densely populated, thus being of geotechnical interest and is currently being investigated through borehole and geophysical data analysis. 52 boreholes were lithologically-geomorphologically analyzed and results from 11 resistivity tomography profiles were considered. Lithostratigraphy of the borehole data was classified into three lithostratigraphic units: Cultural deposits, Pleistocene-Holocene deposits, pre-Holocene bedrock ("Marls of Piraeus"). The deeper unit shows a big depression in the southeastern part of the survey area and a circular sinking (channel) in its north part. These depressions were probably covered by the sea at a time when the southern part of the Piraeus peninsula was an island. This is confirmed by stratigraphical and geophysical investigation in the area where resistivity tomography profiles could be performed. The big southeastern depression is covered by the river sediments implying a high sedimentation rate. © 2013 Elsevier Ltd.
    Scopus© Citations 7  46