Application of GPR for visualising spatial d distribution and internal structures of tsunami deposits ? Case studies from Spain and Greece
Koster, Benjamin; Hadler, Hanna; Vött, Andreas; Reicherter, Klaus
published: Dec 23, 2013
ArtNo. ESP023105704003, Price: 29.00 €
For many years, palaeotsunami research has been based mainly on sedimentological analyses of drill cores and outcrops. Investigating the spatial distribution of palaeotsunami deposits is essential to precisely determine event magnitudes and inundation areas. Mapping the distribution of tsunamites is a challenging task; visualisation by means of drill cores is localised and time consuming. Often, it is also expensive and additional information on the inner structure of tsunamites can not be achieved. Geophysical methods such as ground penetrating radar (GPR) and electrical resistivity tomography (ERT), however, are appropriate methods to determine the spatial variability of palaeotsunami deposits. In this paper, we present GPR data combined with sedimentological methods to rapidly investigate study areas at a high resolution. This approach was tested in two different environments. At the Atlantic coast of southern Spain near Barbate (Cádiz), we investigated a cliff with an elevated tsunamite consisting mainly of coarse gravel, shells and a fining-upward sequence covered by a recent soil. In Greece, the ancient harbour of Lechaion is characterised by coarse-grained sediments covering wide areas of the harbour. GPR data indicate the variable thickness of tsunamigenic layers, channel-like structures of backwash deposits, and a non-planar erosion basement. Abrasion-scours were detected in various places and boulder accumulations at the base of the deposits were detected. We show that shallow GPR is suitable for mapping tsunamites, though this method has certain limits and needs additional information for calibration. Our approach enables improved analyses of tsunamite distribution and stratigraphical architecture.