Geo-Characterization at selected accelerometric stations in Crete (Greece) and comparison of earthquake data recordings with EC8 elastic spectra

Abstract

Abstract:To estimate the seismic response according to Eurocode (EC8) and almost all other national codes, site conditions have to be properly characterized so that soil amplification and the corresponding peak ground motion can be calculated. In this work, different geophysical and geotechnical methods are combined in order to define the detailed ground conditions in selected sites of the Hellenic Accelerometric Network (HAN) in Crete. For this purpose, the geological information of the sites and shear wave velocity, calculated from surface wave measurements, is used. Additionally, ground acceleration data recorded through HAN have been utilized from intermediate depth earthquakes in the broader area of South Aegean Sea.Using the recorded ground motion data and the procedure defined in EC8, the corresponding elastic response spectrum is calculated for the selected sites. The resulting information is compared to the values defined in the corresponding EC8 spectrum for the seismic zone that includes the island of Crete.The comparison shows that accurate definition of ground type through geological, geotechnical and geophysical investigations is important. However, our current comparison focuses on the distribution of values rather than the absolute values of EC8-prescribed spectra, and the results should be considered in this context.

Integrating Earth Observation with Stream Health and Agricultural Activity

“…In environmental magnetism [46], the most used magnetic parameter is magnetic susceptibility (χ), which is the ratio of the induced magnetisation of a sample in the presence of a weak magnetic field to the applied field itself. To characterise the stratigraphy in area I (Table 1), the low-frequency magnetic susceptibility measurements were supplemented with soil properties such as layer thickness (m) from the geological survey and seismic velocity (km/s) and resistivity (Omh.m) from previous studies [47,48], which were re-examined in this work. Agricultural fields in area II (Figure 1b,d) were mapped using GEM-2 from Geophex Ltd. (http://www.geophex.com/Pubs/gem2_-_how_it_works_detailed.htm (accessed on 15 May 2023)) to determine the spatial distribution of two apparent soil properties, i.e., soil apparent conductivity (mS/m) and magnetic susceptibility (10 −5 S.I.).…”