THE CRUSTAL STRUCTURE FROM TELESEISMIC P-WAVE CODA .2. APPLICATION TO DATA OF THE NARS ARRAY IN WESTERN-EUROPE AND COMPARISON WITH DEEP SEISMIC-SOUNDING DATA

The crustal structure beneath a seismic station has a large influence on the P-wave coda recorded by that station. In this study we employ the vertical and radial component of the crustal receiver response to determine the most important features of the crustal velocity structure beneath stations of the NARS array. The receiver response is estimated from the P-wave coda of teleseismic events by deconvolution with a source wavelet and by stacking responses of different events. The crustal velocity structure at the station is derived from these data by non-linear waveform inversion. The responses of some of the NARS stations show anomalous features such as an 'apparent delay' of the first arrival on the radial component relative to the onset on the vertical component. This appears to be a combined effect of very low velocities in the top layer of the model and a strong velocity discontinuity in the uppermost part of the crust. A high amplitude coda on the radial component is observed for stations on a structure with strong S-velocity gradients in the upper crust. The receiver responses of the NARS stations are generally well modelled by the synthetics of the final models of the inversions. The method provides an adequate procedure to estimate the dominant effects of the crustal structure at the site with the models representing the most significant velocity gradients of the crustal structure.