Electrical resistivity tomography mapping of beachrocks: application to the island of Thassos (N. Greece)

Abstract

Electrical resistivity tomography (ERT) technique is widely used in mapping subsurface electrical properties. In this study, ERT was used to map a beachrock outcrop, extended both inland, under beach sediments, and seawards, on and under seafloor sediments. Mapping of beachrock is considered important because it can help evaluate the lateral and vertical extend of the formation. Fast and reliable mapping of beachrocks may contribute in several applications like engineering and construction, coastal management, recreational reformation as well as scientific approaches like coastal evolution research, and palaeo-environmental studies. The outcome of the survey was the mapping of the formation with centimeter precision, especially towards the sea. Special processing was applied to the data in order to constrain the inversion procedure to include the known sea water layer.

Investigation of Natural Beachrock and Physical–Mechanical Comparison with Artificial Beachrock Induced by MICP as a Protective Measure against Beach Erosion at Yogyakarta, Indonesia

“…These velocity layers and resistivity layers were thought to capture the vertical distribution of beachrocks, and the thickness of the beachrocks was estimated to be a maximum of 1 m. In particular, the high resistivity layer in the surface layer at a distance of 3 to 44 m from line-2 corresponded to the beachrock distribution area, where the electrode could only be driven in by about 2 cm. This resistivity layer was almost consistent with that of the beachrock shown by David [4], who reported a resistivity of 2-15 Ωm and a 1-m thickness and Kubo et al [5], who reported a resistivity of 4-20 Ωm and 1-m thickness. A section with high resistivity (46.6 to 78.7 Ωm) was also observed at a distance of 17 to 33 m of the survey line-2, but this can be assumed to correspond to a dry beachrock layer on the ground surface.…”

“…Most of the research on beachrock is related to its geological or chemical properties, and there is very little literature on the underground structure of beachrock. There have been a few cases of electrical exploration on Thassos Island, Greece [4]. To elucidate the formation process of beachrock, it is important to understand the structure of its underground and surrounding area.…”

Geological Exploration of Beachrock through Geophysical Surveying on Yagaji Island, Okinawa, Japan

“…The resistivity of the beachrock on the island of Thassos, Greece, is about 215 ³m according to Psomiadis, 12) whereas that on Yagaji island, Japan, is about 416 ³m (Fig. 6).…”

“…In particular, its underground structure is not yet well understood. One of the few studies of this was by Psomiadis, 12) who used electrical resistivity tomography to map the beachrock on the island of Thassos, Greece. In spite of the general claim that comprehending the underground structure of beachrock is absolutely imperative to elucidating its formation mechanism, research has been restricted to areas near the surface at the seashore because of concerns about damaging the landscape with exploratory boring.…”

Comparison of Sampling Techniques for Isotopic Analysis of Shallow Marine Carbonates

“…1). The beach is 375 m long and reaches width of 25 m (Psomiadis et al, 2009a). Coastal sediments are fine to medium well graded sand with some gravels on the south side where a stream is discharging.…”