1. A method for identifying and displaying random noise from a post-stacked 3-dimensional seismic image using a computer system having a processor, the method comprising the steps of: inputting into said processor data which represents a first 3-dimensional seismic image, wherein said image includes an image structure and noise, and wherein said image is divided into a plurality of pixels each having a value; programming said processor with the following 3-dimensional mask: mask = ( 1 - 2 1 - 2 4 - 2 1 - 2 1 ) , ( - 2 4 - 2 4 - 8 4 - 2 4 - 2 ) , ( 1 - 2 1 - 2 4 - 2 1 - 2 1 ) , where 1, −2, 4, and −8 represent coefficients of the mask having the properties of being zero sum and symmetrical; applying the 3-dimensional mask to each pixel of the received seismic image data using the processor executing a predetermined image processing program, to generate a new 3-dimensional image in which image structure is suppressed such that the new, 3-dimensional image represents noise from the first 3-dimensional seismic image; and displaying the new 3-dimensional image on a display device.