Rayleigh waves normally incident at a continental boundary

Some results of a study of the propagation of monochromatic Rayleigh waves normally incident on the western ocean-continent boundary of the Iberian Peninsula are described. This seismological problem is modelled in two dimensions using the finite element method for periods in the range of 1.5 to 60.0s. The following results for ocean-continent direction of propagation are presented: (i) the estimate of the reflected and transmitted wavefields; (ii) the phase velocity curves for the fundamental mode in the transition zone; (iii) the transmission and reflection coefficients; and (iv) the seismic energy distribution for transmitted and reflected modes. Experimental data from PORTO (PTO), a continental station, and PONTA DELGADA (PDA), an oceanic station, were compared to ascertain the effect on Rayleigh wave propagation across the continental margin. Comparison of the experimental amplitude ratios and transmission factor suggests a thickness of about 4 km for the sediment layer in the western oceanic zone of the Iberian Peninsula.