SUKDMIG3D - Kirchhoff Depth Migration of 3D poststack/prestack data sukdmig3d datain= dataout= [parameters] Required parameters: ttfile file for input tttables Optional Parameters: datain=stdin file for input seismic traces dataout=stdout file for common offset migration output crfile=NULL file for cos theta and ray paths The following 17 parameters describe tttables: (from ttfile header) fxgd= or from header (f1) first x-sample in tttable nxt= or from header (ns) number of x-samples in tttable dxgd= or from header (d1) x-interval in tttable fygd= or from header (f2) first y-sample in tttable nyt= or from header (ntr) number of y-samples in tttable dygd= or from header (d2) y-interval in tttable ixsf= or from header (sdel) x in dxgd of first source nxs= or from header (nhs) number of sources in x ixsr= or from header (swdep) ratio of source & gd spacing iysf= or from header (gdel) y in dygd of first source nys= or from header (nvs) number of sources in y iysr= or from header (gwdep) ratio of source & gd spacing fzs= or from header (sdepth/1000) first depth sample in tttable nzs= or from header (duse) number of depth samples in tttable dzs= or from header (ep/1000) depth interval in tttable nxgd= or from header (selev) x size of the traveltime region nygd= or from header (gelev) y size of the traveltime region multit= or from header (scalel) number of multivalued traveltime The following two parameters are from data header dt= or from header (dt) time sampling interval of input data ft= or from header (ft) first time sample of input data dxm= or from header (d2) mid point spacing of input data Default: output is 5 times finer in depth and 2 times finer in lateral fzo=fzs z-coordinate of first point in output trace dzo=0.2*dzs vertical spacing of output trace (5 times finer) nzo=5*(nzs-1)+1 number of points in output trace (5 times finer) ", fxo=fxgd x-coordinate of first output trace dxo=0.5*dxgd horizontal spacing of output trace (2 times finer) nxo=2*(nxgd-1)+1 number of output traces (2 times finer) fyo=fygd y-coordinate of first output trace dyo=0.5*dygd horizontal spacing of output trace (2 times finer) nyo=2*(nygd-1)+1 number of output traces (2 times finer) Default: poststack migration ", fxoffset=0 first offest in output in x fyoffset=0 first offest in output in y dxoffset=99999 offset increment in output in x dyoffset=99999 offset increment in output in y nxoffset=1 number of offsets in output in x nyoffset=1 number of offsets in output in y ", xoffsetmax=99999 x-maximum absolute offset allowed in migration yoffsetmax=99999 y-maximum absolute offset allowed in migration xaper=nxt*dxgd/2.5 migration lateral aperature in x yaper=nyt*dygd/2.5 migration lateral aperature in y angmax=60 max angle to handle fmax=0.25/dt max frequency in the data jpfile=stderr job print file name pptr=100 print verbal information at every pptr traces ntrmax=100000 maximum number of input traces to be migrated ls=0 point =0 line source =1 Notes: 1. Traveltime tables were generated by program SUTETRARAY (or other ones) on very sparse tetrahedral model, with dimension nys*nxs*nzs *nyt*nxt. 2. Input seismic traces must be SU format and can be any type of gathers (common shot, common offset, common CDP, and so on). ", 3. Migrated traces are output in CDP gathers if velocity analysis is required, with dimension nyoffset*nxoffset*nyo*nxo*nzo. ", 4. If the offset value of an input trace is not in the offset array of output, the nearest one in the array is chosen. 5. Memory requirement for this program is about [nys*nxs*nzs*nyt*nxt+nyoffset*nxoffset*nxo*nyo*nzo+ nys*nxo*nzo*nyt*nxt] 6. Input traces must specify source and receiver positions via header fields tr.sx and tr.gx, as well as tr.sy and tr.gy. Offset is computed automatically. Disclaimer: This is a research code that will take considerable work to get into the form of a a production level 3D migration code. The code is offered as is, along with tetramod and sutetraray, to provide a starting point for researchers who wish to write their own 3D migration codes. Author: Zhaobo Meng, 01/10/97, Colorado School of Mines Trace header fields accessed: ns, dt, delrt, d2 Trace header fields modified: sx, gx