We have simulated seismic wave propagation in models of the subduction zone off the Pacific coast of Mexico using a three-dimensional finite difference method. The results show that a significant part of the energy generated by earthquakes in the subduction zone can be trapped inside a wave-guide generated by the low-velocity material of the accretionary prism. The trapped waves in the simulations appear as long-duration wave-trains that follow the onset of the surface waves, similar to the signature of broadband seismograms recorded by stations along the Pacific coast of Mexico for subduction earthquakes. ¿ 2000 American Geophysical Union