Finite-difference seismograms calculated for the 1971 San Fernando earthquake show strong effects due to lateral variation in sediment thickness in the San Fernando valley and the Los Angeles basin. Using basin structure derived mostly from well logs and teleseismically determined source parameters, two-dimensional SH and P-SV finite-difference calculations reproduce the amplitude and duration of the strong-motion velocities recorded across the Los Angeles and San Fernando basins for the period range of 2 to 10 sec. The edges of basins nearest the seismic source show ground motion amplification up to a factor of 3 over the case without the basin and tend to convert direct shear waves into Love and Rayleigh waves that travel within the basins.

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