Complex Rayleigh waves resulting from deep sedimentary basins

Two earthquakes in northern Mexico recorded by TriNet stations in southern California show complex surface wave propagation through the Salton Trough. Stations contained in a narrow corridor extending from the Salton Trough north towards the Central Valley, California show recorded waveforms with two Rayleigh wave arrivals. The time separation between the Rayleigh wave arrivals is nearly constant beyond the northern edge of the Salton Trough. We are able to reproduce both arrivals with a simple 1-D model of a low velocity, deep basin in the Salton Trough. The slower Rayleigh wave is propagating within the sediments of the basin, while the faster Rayleigh wave propagates mainly in faster, basement rock. Further, we reproduce the constant time separation through the implementation of a simple 2-D model. This 2-D model has a low velocity, deep basin near the source and a crust without a basin at distances greater than 200 km.