BFTR

One can either filter one data set with another, or filter using a namelist file (like the one produce with TRAPLT 6.0.1. The command line arguments are:

 bftr   infil   iswf    filef 
  
 infil:    =input file to be filtered 
 iswf:     =filter source switch  
          0=filters in *.SEG data set  
           (one filter trace for each trace in infil)
          1=single filter specified in namelist file 
      
 filef:    =name of filter data set 
  
 ------Namelist Definitions------- 
 &FILTER   npf=number of points in filter 
           nzph=sample for zero reference 
           fil=f1,f2,f3,f4,....
               (values of filter samples) 
 &end 
  
 NOTE: if you get a core dump, you may have  
       forgotten the &end at the end of the file

The following example shows how to generate filter traces and apply them.

# filter with low pass, 4 pole 12 Hz cut off minimum phase
bdum c008.seg .10
bfil bdumc008.seg 0 4 12. 1
bplt bfilbdum.seg 2 0 0 1 100 0.0 .4 1 2E-2 200

# apply low passed by convolving bfilbdum.seg with c008.seg
bftr c008.seg 0 bfilbdum.seg
bequ bftrc008.seg 0 1.
bplt bequbftr.seg 2 0 0 1 100 0.0 1. 1 2 200

The procedure:

1. BDUM creates a file with an impulse at 0.1 seconds, the template is the field data file, c008.seg. The output is bdumc008.seg.
2. BFIL filter the impulse file with a low pass filter, 4 pole, 12 Hz cutoff, minimum phase. Output is bfilbdum.seg Figure 95A.
3. BFTR filter c008.seg with the file, bfilbdum.seg Figure 95B.

Figure 95: (A) BDUM->BFIL: Filtered file of impulses. (B) BFTR: Filter field data with filtered impulse file. Input data c008.seg are same as in Figure 91A.

The other alternative would be to run TRAPLT on file bfilbdum.seg and copy the namelist section to a file, call it filter.dat. We must add a &end statement not provided by TRAPLT. The filter.dat file will look like this:

 &filter
  npf=  221, nzph=    1
  fil=
   0.0000,   0.0000,   0.0000,   0.0000,   0.0000,   0.0000,   0.0000,   0.0000,
   0.0000,   0.0000,   0.0000,   0.0000,   0.0000,   0.0000,   0.0000,   0.0000,
   0.0000,   0.0000,   0.0000,   0.0000,   0.0000,   0.0001,   0.0003,   0.0007,
   0.0015,   0.0027,   0.0044,   0.0067,   0.0095,   0.0130,   0.0172,   0.0220,
   0.0276,   0.0338,   0.0406,   0.0481,   0.0563,   0.0650,   0.0743,   0.0842,
   0.0945,   0.1054,   0.1166,   0.1282,   0.1401,   0.1524,   0.1648,   0.1775,
   0.1903,   0.2032,   0.2161,   0.2290,   0.2419,   0.2548,   0.2675,   0.2800,
   0.2923,   0.3044,   0.3162,   0.3278,   0.3389,   0.3498,   0.3602,   0.3702,
   0.3798,   0.3889,   0.3975,   0.4056,   0.4132,   0.4203,   0.4269,   0.4329,
   0.4384,   0.4433,   0.4477,   0.4515,   0.4547,   0.4574,   0.4596,   0.4612,
   0.4622,   0.4628,   0.4627,   0.4622,   0.4612,   0.4597,   0.4577,   0.4552,
   0.4523,   0.4489,   0.4451,   0.4409,   0.4363,   0.4313,   0.4260,   0.4203,
   0.4143,   0.4080,   0.4015,   0.3946,   0.3875,   0.3801,   0.3726,   0.3648,
   0.3569,   0.3488,   0.3405,   0.3322,   0.3237,   0.3151,   0.3064,   0.2977,
   0.2889,   0.2801,   0.2712,   0.2624,   0.2535,   0.2447,   0.2359,   0.2271,
   0.2184,   0.2098,   0.2013,   0.1928,   0.1844,   0.1761,   0.1680,   0.1599,
   0.1520,   0.1442,   0.1366,   0.1291,   0.1218,   0.1146,   0.1076,   0.1007,
   0.0940,   0.0875,   0.0811,   0.0750,   0.0690,   0.0632,   0.0575,   0.0521,
   0.0468,   0.0417,   0.0368,   0.0321,   0.0275,   0.0232,   0.0190,   0.0150,
   0.0112,   0.0075,   0.0040,   0.0007,  -0.0025,  -0.0054,  -0.0083,  -0.0109,
  -0.0135,  -0.0158,  -0.0181,  -0.0201,  -0.0221,  -0.0239,  -0.0255,  -0.0271,
  -0.0285,  -0.0298,  -0.0309,  -0.0320,  -0.0330,  -0.0338,  -0.0345,  -0.0352,
  -0.0357,  -0.0362,  -0.0366,  -0.0368,  -0.0371,  -0.0372,  -0.0372,  -0.0372,
  -0.0372,  -0.0370,  -0.0368,  -0.0366,  -0.0363,  -0.0359,  -0.0356,  -0.0351,
  -0.0347,  -0.0341,  -0.0336,  -0.0330,  -0.0324,  -0.0318,  -0.0311,  -0.0305,
  -0.0298,  -0.0291,  -0.0284,  -0.0276,  -0.0269,  -0.0261,  -0.0254,  -0.0246,
  -0.0239,  -0.0231,  -0.0223,  -0.0216,  -0.0208,  -0.0200,  -0.0193,  -0.0185,
  -0.0178,  -0.0171,  -0.0164,  -0.0156,  -0.0149,
&end

The commands for the alternative would be:

 traplt bfilbdum.seg 0.09 .2 1 0 1
 bftr c008.seg 1 filter.dat
 bequ bftrc008.seg 0 1.
 bplt bequbftr.seg 2 0 0 1 100 0.0 1. 1 2 200

NOTE: The TRAPLT command above does not start listing at 0.0 seconds, but at .09 seconds. This produces a namelist file with less delay, and this is evident comparing the two different approaches.

Figure 96: (B) BFTR: same as in Figure 95B. (C) BFTR: Filter field data with namelist file, filter.dat. Input data c008.seg are same as in Figure 91A. Note the different delay in time.