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Summary The soil characteristics in the area located south of Chania city in Crete (Greece) is investigated to get insight about the dynamic behaviour of the ground during an earthquake vibration and to form a basis for further studies. To implement this scope, multi-channel analysis of surface wave method at 4 sites in the summer of 2015 and ambient noise data at 113 sites in the summer of 2016 were collected. The analysis results of the geophysical data show relatively high seismic amplifications and relatively weak resistance to an earthquake vibration in the central and the coastal sites.

This paper presents the application of spectral induced polarization (SIP) method in a controlled laboratory experiment using known fluid concentrations. Specifically, we employed different fluid samples with variable concentration in order to record the temporal change of SIP response over time and test the sensitivity and reliability of SIP method. The SIP method has proved to be an important qualitative monitoring tool for assessing the environmental quality in contaminated lands.

A geophysical survey was conducted at Bafra, Samsun, Turkey, Greece in order to support the geological and hydrogeological studies of the existing phenomenon of seawater intrusion. This survey employed seismic refraction tomography (ST), time domain electromagnetic (TDEM) and geoelectrical methods. The later, consisted of Electrical Resistivity Tomography (ERT). The objective of this survey was to image the saltwater intrusion at this area and map possible favorable sea water pathways. We present the interpretation of geophysical data obtained under the research project ClearWater project. We applied both individual and joint inversion of electric and seismic data from Bafra. At Bafra, the geophysical survey provided images of the saltwater intrusion which is present at the north eastern of the study area. These geophysical methods proved useful as prediction and prevention tools in qualitative characterization of water bearing formations for an optimum groundwater management plan for the Bafra basin.

The last decade, the use of geophysical surveys prior to completion of the initial subsurface monitoring and characterization for constructing wind parks, is very common. Geophysical models can provide critical, valuable, accurate and reliable information concerning the status of the ground on the site where the wind turbine are going to be founded and such information can be used by the engineers in the most appropriate and cost-effective way. This paper presents the use of surface wave method for the exploration of the subsurface in order to define the optimum places for wind turbine foundation.

This paper presents the application of self-potential (SP) method in environmental application. The resulted SP model was compared with the resulted tomographic electrical resistivity models which acquired at the same time period with SP data. Both geophysical methods applied in Western Crete in Chania territory to delineate contaminants movements from a waste disposal site to the main river of Chania basin through the alluvial permeable formation. The main purpose of the SP method was the determination of the subsurface contaminants flow direction. The final resulted images showed a good correlation with geoelectrical resistivity model. The self-potential method has proved to be an important qualitative monitoring tool for assessing the environmental quality in contaminated lands.

Olive oil production is one of the most important activities in the Mediterranean area and in Greece in particular. Olive oil production generates a large volume of liquid wastes which can cause severe pollution due to the high organic and in-inorganic load that they convey. In this work we assess the ability of time-lapse electrical resistivity tomography (ERT) technique to monitor Olive-oil mills' wastes (OOMW) movement into an aquifer. Test involve performing extensive synthetic modelling using computer generated models for cross-hole ERT arrangements and applying various 4D time lapse inversion processing to the monitoring data. Further, 4D time lapse inversion was performed to cross-hole ERT data obtained during a tank experiment which involved simulation of OOMW movement into a saturated aquifer. Results validate the applicability of cross-hole time lapse ERT to monitor OOMW movement and help to decide ways for optimum data processing and collection.

Summarization: Recent advances in Seismic Codes increased the necessity in Engineering Geophysics to use surface wave analysis as a tool. The shear wave velocity profile had to be resolved to calculate the site amplification in case of an earthquake event, necessary also for seismic hazard studies. In our approach we present the results from Surface Wave data acquired in different site in Crete Island (Greece) at strong motion sites. Passive and Active data at linear and circular geometries have been analyzed and the corresponding processing and inversion results are compared. Although one would comment that there are discrepancies on Dispersion Curve results the resulted ground profiles up to a shallow depth show considerable agreement. However, this is site dependent and in order to increase the accuracy and reliability of results one should be careful with the assignment of different modes in surface wave analysis and also combine the results provided. Presented on

Summarization: A geophysical survey was conducted at Tybaki, Crete, Greece in order to support the geological and hydrogeological studies of the existing phenomenon of seawater intrusion. This survey employed seismic refraction, transient electromagnetic (TEM) and geoelectrical methods. The later, consisted of Vertical Electrical Sounding (VES) and Electrical Resistivity Tomography (ERT). The objective of this survey was to image the saltwater intrusion at this area and map possible favorable sea water pathways. We present the combined interpretation of vintage geophysical data obtained under the research project MEDIS and the ClearWater project data. At Tybaki, the geophysical survey provided images of the saltwater intrusion which is present at the north west of the basin Παρουσιάστηκε στο: 20th European Meeting of Environmental and Engineering Geophysics

Electrical resistivity tomography (ERT) has long been recognized to exhibit the potential to significantly improve characterization of sites contaminated with dense non-aqueous phase liquids (DNAPLs). However, the technique has not become a common tool for mapping such contaminants due to the complexity of the DNAPL target coupled with the inherent limitations of the commonly used surface and cross-hole ERT configurations. The objective of this work is to evaluate the potential of surface-to-horizontal borehole (S2HB) ERT for mapping the spatio-temporal evolution of DNAPL mass during remediation. A coupled DNAPL-ERT model was employed to provide an initial, theoretical evaluation of S2HB ERT, relative to surface ERT, for monitoring the remediation of a realistic, field-scale DNAPL source zone. A laboratory experiment was then performed to demonstrate the S2HB ERT approach for a real system involving a changing NAPL distribution over time. Four-dimensional ERT inversion was employed for both numerical and experimental data to generate time-lapse resistivity images of the subsurface regions experiencing NAPL changes. Results demonstrate significantly improved resistivity imaging with S2HB ERT and its potential as a non-invasive DNAPL site tool for mapping DNAPL mass changes during remediation.