ALBERT

Description: 〈span〉〈div〉SUMMARY〈/div〉Extracting Moho-reflected 〈span〉P〈/span〉 waves from vertical component seismic noise to determine crustal thickness has become a common method over the last years. In this study, we image the reflectivity below various stations across Central and Eastern Europe and extract Moho-reflected 〈span〉S〈/span〉 waves using horizontal component correlations. In addition to horizontal component autocorrelations, we include single-station cross-correlations in the process of obtaining crustal thickness estimates from seismic noise for the first time. For each station, a lag time range for the reflectivity change associated with the Moho is obtained with the help of prior information, and lag times are converted to depth to give a crustal thickness range. In addition, we calculate 〈span〉vP〈/span〉/〈span〉vS〈/span〉 ratios from the picked reflectivity changes on the vertical and horizontal component correlations.On an average 8.5 months of data are needed for the autocorrelations to obtain stable results. For the cross-correlations, on average 1.3 yr of data are required to reach stability. The obtained Moho depth ranges compare well with results determined with vertical component autocorrelations, receiver functions and provided in the European Moho depth map. The 〈span〉vP〈/span〉/〈span〉vS〈/span〉 ratios show a large variability and do not give reliable results. In addition to identifying reflectivity changes in 〈span〉S〈/span〉 waves on the horizontal component correlations, it is also possible to observe these reflectivity changes on vertical component correlations, as well as 〈span〉P〈/span〉-wave reflectivity changes on the horizontal component correlations, for some stations. Furthermore, we can detect 〈span〉P〈/span〉- to 〈span〉S〈/span〉- or 〈span〉S〈/span〉- to 〈span〉P〈/span〉-converted phases on cross-correlations of mixed horizontal and vertical components. From this we conclude that the incidence of the waves reaching the surface is not generally vertical, leading to errors when converting lag time to depth and in the calculation of the 〈span〉vP〈/span〉/〈span〉vS〈/span〉 ratios. Lag time differences between the Moho arrivals on the two horizontal component autocorrelations can be interpreted in terms of azimuthal anisotropy in the crust.〈/span〉

Description: 〈span〉Seismic interferometryseismic noisebody wavescrust〈/span〉

Description: 〈span〉〈div〉Summary〈/div〉Extracting Moho-reflected 〈span〉P〈/span〉-waves from vertical component seismic noise to determine crustal thickness has become a common method over the last years. In this study, we image the reflectivity below various stations across Central and Eastern Europe and extract Moho-reflected 〈span〉S〈/span〉-waves using horizontal component correlations. In addition to horizontal component autocorrelations, we include single-station cross-correlations in the process of obtaining crustal thickness estimates from seismic noise for the first time. For each station, a lag time range for the reflectivity change associated with the Moho is obtained with the help of prior information, and lag times are converted to depth to give a crustal thickness range. In addition, we calculate 〈span〉v〈/span〉〈sub〉P〈/sub〉/〈span〉v〈/span〉〈sub〉S〈/sub〉-ratios from the picked reflectivity changes on the vertical and horizontal component correlations. On average 8.5 months of data are needed for the autocorrelations to obtain stable results. For the cross-correlations, on average 1.3 yr of data are required to reach stability. The obtained Moho depth ranges compare well with results determined with vertical component autocorrelations, receiver functions, and provided in the European Moho depth map. The 〈span〉v〈/span〉〈sub〉P〈/sub〉/〈span〉v〈/span〉〈sub〉S〈/sub〉-ratios show a large variability and do not give reliable results. In addition to identifying reflectivity changes in 〈span〉S〈/span〉-waves on the horizontal component correlations, it is also possible to observe these reflectivity changes on vertical component correlations, as well as 〈span〉P〈/span〉-wave reflectivity changes on the horizontal component correlations, for some stations. Furthermore, we can detect 〈span〉P〈/span〉- to 〈span〉S〈/span〉- or 〈span〉S〈/span〉- to 〈span〉P〈/span〉-converted phases on cross-correlations of mixed horizontal and vertical components. From this we conclude that the incidence of the waves reaching the surface is not generally vertical, leading to errors when converting lag time to depth and in the calculation of the 〈span〉v〈/span〉〈sub〉P〈/sub〉/〈span〉v〈/span〉〈sub〉S〈/sub〉-ratios. Lag time differences between the Moho arrivals on the two horizontal component autocorrelations can be interpreted in terms of azimuthal anisotropy in the crust.〈/span〉