Numerical simulation of the 1969 Portuguese tsunami by a finite element method

On 28 February 1969, the coasts of Portugal, Spain and Morocco were affected by sea waves generated by a submarine earthquake (Ms = 7.3) with its epicenter located off Portugal. The propagation of this tsunami has been simulated by a finite element numerical model solving the Boussinesq equations. These equations have been discretized using the finite element Galerkin method and a Crank-Nicholson scheme in time. The model is validated by investigating the propagation of a solitary wave over a flat bottom. The grid sizes for the 1969 event have been determined by one-dimensional tests offshore and in shallow water regions. The two-dimensional simulation of the 1969 tsunami is carried out using the hydraulic source calculated from the geophysical model of Okada and seismic parameters of Fukao. The modeled waves are compared with the recorded ones with respect to travel times, maximum amplitudes and periods of the signal. The comparison between Boussinesq and shallow-water models shows that the effects of frequency dispersion are minor. Good agreement is found for most of the studied gauges.