PROCESSING AND INVERSION OF LONG-PERIOD SURFACE-WAVE DATA COLLECTED IN THE IBERIAN PENINSULA

Several filtering techniques have been used to remove the effects of multipathing and modal contamination, and to isolate the fundamental mode from Rayleigh wavetrains. Group velocity data are obtained by means of the multiple‐filter technique. A time‐variable filter has allowed the influence of noise as well as the interference produced by higher modes to be removed. Multiple filtering is then used again to compute group velocities at each station. the interstation group velocity for the fundamental mode Rayleigh wave is estimated according to the velocities at two stations. Frequency‐domain Wiener deconvolution is used to compute the phase velocity between two stations. the well‐known three‐station method is applied to correct the distances travelled by the waves across the array and therefore to determine interstation phase and group velocities in a more accurate manner. On the other hand, lateral refraction at the Atlantic continental edge of the Peninsula is also studied. Phase velocities are corrected for the anelastic effect. Inversion of the interstation Rayleigh wave phase velocities is then made in accordance with generalized inversion theory to obtain theoretical 2‐D layered earth models. In this paper, these methods are applied to Rayleigh waves generated by teleseismic events propagating across the Iberian Peninsula and recorded at WWSSN stations. As a consequence, new and principal features for the Iberian lithosphere‐asthenosphere system are obtained. A very interesting feature of the the Iberian lithosphere was found‐a low‐velocity layer directly under the Moho, between 39 and 64 km depth, with shear velocities ranging from 4.12 to 4.37 km s‐1. the Iberian asthenosphere, which lies between 100 and 180km depth, is not an homogeneous layer and shows a negative velocity gradient from top to bottom together with a sudden increase in shear velocity beneath the low‐velocity zone. Copyright © 1990, Wiley Blackwell. All rights reserved