1st Croatian Conference on Earthquake Engineering 1CroCEE 2021

Definition of seismo-geological characteristics of a terrain is of a great importance when it comes to selection of strong-motion station sites. Local site conditions can modify the amplitude-frequency content of the seismic motion during an earthquake. Therefore, site characterization is very significant for correct analysis and use of earthquake records.
Geophysical surveys using surface seismic methods were performed at few different characteristic locations in the territory of North Macedonia. The potential sites were, first of all, selected based on off-site (office) studies, which include parameters such as geographical region of interest, seismo-geological characteristics, seismic noise, accessibility, electricity, communication, transport, etc.
Surface seismic methods represent widely accepted geophysical methods for seismo-geological modeling and evaluation of parameters that have a direct influence on the site response during an earthquake, such as seismic velocities and topography of bedrock. At each selected location, time and cost-effective surveys were conducted by joint acquisition of seismic refraction, seismic reflection and Multichannel Analysis of Surface Waves (MASW) data. Microtremor measurements for HVSR (Horizontal to Vertical Spectral Ratio) analysis were also performed for definition of the predominant frequency and joint inversion of the dispersion and HVSR curve.
The final results from this integrated seismic survey approach are 1D Vs and 2D Vp and Vs models that, according to the variation of Vp and Vs velocities, map the thickness variation in non-consolidated sediments as well as 2D reflective sections, which define the weathered zones, discontinuities and faults in rocks.