Now showing 1 - 2 of 2
  • 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  121
  • 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  55