Details

Autor(en) / Beteiligte

• Boxberger, Tobias

Titel

A Comparison of Different Seismological and Geotechnical Parameters for Site Characterization

Ort / Verlag

ProQuest Dissertations Publishing

Erscheinungsjahr

2018

Link zum Volltext

• ProQuest

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• The geometry of the subsoil structure, the soil types involved and the variation in their properties with depth, lateral discontinuities and surface topography are causes of lateral variation in earthquake-induced ground motion, over relatively small scales, referred to as "site effects" The modification of ground motion can manifest itself through amplification at particular frequencies (the lowest one defining the fundamental resonance frequency), depending on the thickness and the velocity structure of the uppermost layers, and deamplification due to the competitive effect of the attenuation of the wavefield in shallow soft layers. Therefore, a detailed characterization of the properties of shallow geological structures in terms of the fundamental resonance frequency f0 , local shear wave (S-wave) velocity structure and a quality factor (Qs ) profile, which quantifies the effects of anelastic attenuation on the seismic wavelet, is necessary. Over the last decades, techniques based on the analysis of seismic noise, which is generated by natural and anthropogenic sources, have been found to have the potential to significantly contribute to site effect evaluation as they can provide sufficiently accurate estimates of the underlying Vs profile. Recently, modification of the same methods have proved to be able to provide realistic Qs versus depth estimations. A now generally adopted approach in seismic hazard assessment for mapping seismic site conditions is estimating the average shear wave velocity in the uppermost 30 m (Vs30 ) as a proxy of the site response. This approach was also applied to the quality factor within the uppermost 30 m (Qs30 ). In this thesis, data sets of seismic noise recorded in different regions of Europe and Central Asia by microarrays of seismic stations was used to calculate both Vs and Qs profiles. By applying innovative analysis techniques, it is shown that the values are consistent and that seismic noise analysis has the potential to provide a comprehensive (Vs and Qs ) description of the geological structure below a site.