Mapping and investigating directional effects through analysis of microtremors: the case of palaeo-Piniada valley, central Greece.

*Corresponding Author

Abstract

The Horizontal to Vertical Spectral Ratio, or “HVSR”, has become popular in the last decades, especially because it leverages on inexpensive equipment and minimal workforce. One of the most attractive aspect is that elastic shear wave resonance frequency of a sedimentary basin can be retrieved and readily used to obtain an estimate of the depth of the major elastic impedance contrast(s). Additionally, the shear wave velocity (Vs) distribution can be obtained through dedicated inversion procedures. We performed more than 300 microtremor measurements across the Piniada Valley (Central Greece), distributed along and between several transects planned roughly perpendicular to the mean valley trend. Such an effort was carried out to understand the palaeogeographic and tectonic evolution of this area by first estimating the geometry at depth of the bedrock underlying the fluvial deposits of the Pinios River. Initially, the estimate was performed using a simplified approach, obtaining an approximate 3D model. We performed the directional analysis to investigate if effects connected to the sloping bedrock at the valley borders can be recognized. Finally, HVSR curves were inverted to refine the subsurface model and to estimate its uncertainty.The Horizontal to Vertical Spectral Ratio, or “HVSR”, has become popular in the last decades, especially because it leverages on inexpensive equipment and minimal workforce. One of the most attractive aspect is that elastic shear wave resonance frequency of a sedimentary basin can be retrieved and readily used to obtain an estimate of the depth of the major elastic impedance contrast(s). Additionally, the shear wave velocity (Vs) distribution can be obtained through dedicated inversion procedures. We performed more than 300 microtremor measurements across the Piniada Valley (Central Greece), distributed along and between several transects planned roughly perpendicular to the mean valley trend. Such an effort was carried out to understand the palaeogeographic and tectonic evolution of this area by first estimating the geometry at depth of the bedrock underlying the fluvial deposits of the Pinios River. Initially, the estimate was performed using a simplified approach, obtaining an approximate 3D model. We performed the directional analysis to investigate if effects connected to the sloping bedrock at the valley borders can be recognized. Finally, HVSR curves were inverted to refine the subsurface model and to estimate its uncertainty.