We have analyzed the long-period Rayleigh and Love waves that were generated by four recent large earthquakes (New Ireland of 18 March 1983; Costa Rica of 4 April 1983; Honshu of 26 May 1983; and Chagos Islands of 30 November 1983).
Our records are those of the three-component very long-period stations (SSB, PCR, PAF, and TAM) of the GEOSCOPE network, that were in operation in 1983.
Available information from transverse and radial components is obtained; preliminary results concerning the fundamental modes of Love and Rayleigh waves, the first toroidal overtone, the second, and the third spheroidal higher mode are presented. For each of these particular modes, the phase velocities and sometimes the Q quality factors have been obtained, and the methods of data reduction are described in detail for future reference. The examples shown demonstrate, in particular, the benefits to be expected from a modern three-component very long-period network, as well as from original station locations.