Cerdanya basin characterisation using H/V and F-K seismic noise methods

Abstract

Seismic noise methods are nowadays widely used in geophysics being easy and non-invasive techniques to characterise the subsoil. In the present study I use F-K and H/V methods to process data collected on the Cerdanya Basin during 2012 by ICGC. The main objective has been to determine the thickness of the basin sedimentary materials in two different locations: Ger, above the mountain, and an aerodrome, down the valley. H/V method uses single geophones to record triaxial seismic noise vibrations. The data processing is able to find the resonant frequency of the soil, which is a good indicator of the sedimentary material thickness but does not provide a numerical value. On the other hand, F-K method goes further and uses arrays of registering stations to acquire data. The processing and inversion of this seismic noise gives the Rayleigh waves propagation velocity for each subsoil layer, giving way to a good characterisation of the material that conforms them. This characterisation allows us to estimate the rocky basement depth, which finally becomes in 360 meters for the aerodrome and 100 meters for Ger. The final processing method performed has been to combine the results from the two previous methods to achieve a second thickness numerical measure, which approaches to the previous results obtained.