1. A computer-readable medium containing a program for removing aliasing noise from three-dimensional (3-D) time-slowness (tau-P) data, which, when executed by a processor, performs operations comprising: decomposing the tau-P data into a plurality of frequency bands, wherein a template frequency band in the plurality of frequency bands does not contain aliasing noise and at least a portion of the other frequency bands constitute a subset of frequency bands for processing; calculating an envelope for the template frequency band and for each of the frequency bands in the subset to generate a plurality of envelope cuboids; for each frequency band in the subset from the lowest to the highest frequency band in the subset, multiplying an envelope cuboid associated with the present frequency band with an envelope cuboid associated with an adjacent lower frequency band or with the template frequency band to produce an envelope mask for the present frequency band, saving the envelope mask as the envelope cuboid associated with the present frequency band, and multiplying the envelope mask for the present frequency band with the tau-P data for the present frequency band to produce processed tau-P data for the present frequency band such that the aliasing noise is removed; and summing the tau-P data for the template frequency band and the processed tau-P data for each of the frequency bands in the subset to produce tau-P data without aliasing noise.