Identifying sedimentary structures and spatial distribution of tsunami deposits with GPR - examples from Spain and Greece

Abstract

Shallow drilling in coastal areas like southern Spain and different parts of Greece (Corinth region and Argolis Gulf) proved evidence for tsunamis. Sedimentary analyses were conducted to identify tsunamigenic deposits, but did not reveal sedimentary structures or spatial distribution of tsunamites in a regional scale. Since drilling is time-intensive and expensive (depending on extend), this method can by far not cover an entire coastal area. On the other hand, distribution and preservation of tsunamigenic deposits seems to be highly variable. We used ground penetrating radar (GPR) in combination with electrical resistivity tomography (ERT) measurements and sedimentological research methods for tsunamite detection in Greece and Spain. The combination of these three methods enables an improved interpretation of the results and 3D visualization, which give clues for tsunamite distribution and sediment architecture. GPR data indicate unconformable thicknesses of tsunamigenic beddings, channel-like structures (back wash deposits), in some extent chaotic erosion basement, as well as abrasion-scours in various places, and boulder accumulation inside the deposits. In the future, GPR and other shallow geophysical methods will be used to detect run-up distances and typical sediment structures.