Estimation of glacier thicknesses and basal properties using the horizontal-to-vertical component spectral ratio (HVSR) technique from passive seismic data

Microtremor measurements and the horizontal-to-vertical spectral ratio (HVSR) technique,generally used for site effect studies as well as to determine the thickness of soft sedimentary layers, caneffectively be applied to map the thickness of glaciers. In this work the radio-echo sounding, geoelectricand active seismic methods, widely employed to image the earth interior, are applied to verify the reliabilityof the HVSR technique in Alpine and Antarctic glacial environments. The technique has been usedto analyze passive seismic data from glaciers of the Adamello and Ortles-Cevedale massifs (Italy), theBernese Oberland Alps (Switzerland) and from the Whillans Ice Stream (West Antarctica). Comparingwith the results obtained from the different geophysical imaging methods, we show that the resonancefrequency in the HVSR spectra correlates well with the ice thickness at the site, in a wide range from afew tens of meters to more than 800 m. The reliability of the method mainly depends on the coupling ofsensors at the glacier surface and on the basal impedance contrast. This passive seismic technique offersa logistically efficient and cost effective method to map glacier and ice-sheet thicknesses. Moreover,under certain conditions, it allows reliable estimations of the basal seismic properties.