1. A method for inferring presence of hydrocarbons from a seismic data volume representing a subsurface region, using local statistical distributions of seismic data values, comprising: (a) using two moving windows of user-selected size and shape, one being a pattern window and the other a sampling window larger than the pattern window, wherein the sampling window moves to different locations in the seismic data volume to sample the seismic data volume, and at each location of the sampling window the pattern window moves about within the sampling window; (b) for each sampling window location, computing a statistical distribution of seismic data values for all pattern windows contained within the sampling window; (c) from the statistical distribution within a sampling window, computing an outlier probability or residue for each sampling window; and (d) interpreting the outlier probabilities or residues for the sampling windows for indications of hydrocarbon presence within the subsurface region; wherein at least one of (a)-(d) is performed using a computer.