# The Contribution of Near-Surface Geophysics for the Site Characterization of Seismological Stations
## 3 Application of the Geophysical Surveys and Processing Results
### Seismological Station at Epidavros, Argolis (EPID)  
Station _EPID_, located at Kalamiou monastery (Figure 18), near the town of Epidavros in eastern Peloponnese, was deployed on 8 October 2010. The site is important for the monitoring of the seismic activity in the southern Saronikos Gulf, which hosts the Methane volcano, at the north-western end of the Hellenic volcanic arc. Station _EPID_ is currently equipped with a _Guralp CMG-DM24S6-EAM_ datalogger and a _CMG-40T/30s_ seismometer. The area consists of undivided Quaternary sediments and soils (_Q_), which overlie the Middle-Upper Triassic chert limestones (_T2-4 k, km_) and the Lower Triassic trachytes and traclytic tuffs (_\(\tau\)_, f_), as described by [74].  
Figure 17: SRT and MASW (**top**) and ERT (**bottom**) sections at the site of the seismological station _ATAL_.  
Figure 18: Location of the seismological station _EPID_ and the geophysical measurements along with the geology of the area.  
The HVSR curves for station _EPID_ (Figure 19) show a clear but broad peak frequency at \(f\) = 6.5 Hz, with \(A\) = 2.3 \(\pm\) 0.8. The base amplification level for station _EPID_ is close to 0.8, which is lower than unity, indicating that the amplification factors could be underestimated by 0.2. Higher values of amplification are acquired when using a square average for the horizontal components. In that case, the base level is equal to 1.1, and the peak frequency at 6.5 Hz has an amplification factor equal to 2.5 \(\pm\) 0.8.  
At the seismological station of Epidavros (_EPID_), three seismic layers were identified through the SRT technique (Figure 20). The first and second layers develop after the first 5.0 m of the SRT section, with an average thickness of 2.0 m and 1.0 m, respectively. Their P-wave velocity values were determined to be equal to \(V_{P1}\) = 600 m/s and \(V_{P2}\) = 750 m/s. Finally, below these layers, the existence of the seismic bedrock was defined with \(V_{P3}\) > 800 m/s. The MASW technique (Figure 20) revealed a seismic bedrock shear-wave velocity of 350 m/s and a V\({}_{\text{S30}}\) value equal to 393 m/s. In Figure 20, the 2D distribution of the subsurface resistivity is also presented. At the central parts of the section and at depths above 4.0 m, a relatively resistant (>600 Ohm.m) formation is investigated. Below that, a more conductive formation dominates across the section with a resistivity value lower than 300 Ohm.m.  
Figure 19: Average HVSR curves (solid lines) determined for station _EPID_ on different days, from 60 s long windows selected after the application of STA/LTA anti-triggering on 6 h long records. Circles denote the global frequency on each curve, while diamond symbols mark the average of the frequency band denoting the range of peak frequencies of the HVSR lines from the individually selected windows (light/dark gray band in Figure 2b). Squares mark the prominent global and secondary peak frequencies recognized from the HVSR spectra, with error bars indicating the uncertainty of the amplification factor (Table A1).