PROCESS WEIGHT (TRACE WEIGHTING, KILLING, REVERSING) Parameters, alphabetically: fno hdr ihdr inverse lhdr lno lprint twp type w weight xwp Document Date: 7 January 2007 Modifications: June 2006 - Add parameter TYPE and weighting by inverse standard deviation. Nov. 2005 - Change LNO to default to FNO (set to FNO on every list) PROCESS WEIGHT weights individual traces by multiplying the entire trace by a constant (scalar multiply). A weight of 1. Results in no amplitude change on the trace. A weight of 0. Results in the trace being killed. A weight of -1. Results in the trace being reversed in polarity. All traces have a default weight of 1. This means that only those traces specified by the user will be weighted. Weights are not spatially varied, thus only those shots actually specified will be weighted. Each parameter list must be terminated with the word END. The entire set of weight parameters must be terminated by the word END. THE PARAMETER DICTIONARY --- --------- ---------- FNO - The first shot (or rp) to apply the weights to. Shot (rp) numbers must increase monotonically. Preset = 1 LNO - The last shot (rp) number to apply the weights to. LNO must be larger than FNO in each list and must increase list to list. Default = FNO (reset to FNO on each list unless LNO is given). XWP - Range-weight-pairs. A list of range and weight pairs. XWP must be given with increasing ranges. The program computes the absolute value of both user ranges and data ranges. e.g. xwp 1000 3.0 2000 0. - Traces with ranges exactly equal to 1000 will be multiplied by 3, and traces with a range of exactly 2000 will be multiplied 0. (i.e. killed). All other traces will not be multiplied. Default = all 1. TWP - Trace number-weight-pairs. A list of trace numbers (of a shot or rp) and weights (listed in pairs). ONLY THOSE TRACES SPECIFIED WILL BE WEIGHTED. Trace numbers must increase within each list. e.g. twp 4 -1. 20 0. indicates that trace 4 will be inverted in polarity and trace 20 will be killed. Default = all 1. WEIGHT - The multiplier for all traces of the specified shot/rp (fno). The default value is 1., which means that the weight is applied to shot FNO to LNO, then reset to 1. (the default value). Default = 1. e.g. FNO 1234 weight 0 end W - An abbreviation for weight. Equivalent to weight. Default = 1. e.g. fno 1234 w -1 end HDR - Specifies the index of the SEG-Y trace header floating point word as the trace scalar multiplier. Each trace is independent. e.g. hdr 55 causes every amplitude to be multiplied by the contents of the 55th floating point word in the SEGY trace header. LHDR - Specifies the index of the 32 bit integer SEG-Y trace header word as the trace scalar multiplier. Each trace is independent. IHDR - Specifies the index of the 16 bit integer SEG-Y trace header word as the trace scalar multiplier. Each trace is independent. INVERSE - A YES/NO switch indicating that the inverse or reciprocal of the given weight should be used. i.e. the multiplier becomes a divisor. Preset = no e.g. inverse yes TYPE - The type of weight to apply. = SDEV, The inverse of the standard deviation is used as a scalar multiplier for each trace. Preset = not given (use w or weight) e.g. type sdev LPRINT - Programmer's debug switch. = 8, The weight applied to each trace is printed. = 16, All the statisics are printed when TYPE SDEV is given. END - Terminates each parameter list. Note ***** 1) In order to apply the same set of weights to all shots (rps), LNO must be set to a very large number. e.g. LNO 32767 2) a maximum of 100 twp or xwp pairs may be given. 3) If multiple weights are give a a trace, they are multiplied together before the trace multiplication is performed. E.G. if w 2 and type sdev results in a weight of 15, the total weigth applied is 30. Example 1: process weight fno 0 lno 999999 xwp 1228 -1 1408 0 end end Will reverse the polarity of all traces having a range of 1228, and will kill all traces with a range of 1408, on shots (rps) 1 through 32767. Example 2: Weight by offset (ala GECO) procs .... header weight ..... header r60 = l10 + 6100 # 6100 is the far offset r59 = l10 / r60 end end weight fno 0 lno 99999 hdr 59 end end Example 3: Weight by inverse standard deviation. weight fno 0 lno 999999 type sdev end # apply to ALL records 0-999999 end Copyrighted (c) by: Paul Henkart, Scripps Institution of Oceanography, November 1980 ALL RIGHTS RESERVED.Go to the list of seismic processes. Go to SIOSEIS introduction.