BVSP

This code reads a down-hole survey in BSEGY seismic format. It fits a 3 layer velocity model to the arrival times. The output *.lst file identifies the first arrivals as direct or refracted ray paths.

 bvsp infile itmax zmin zmax
 infile:   =input file name 
 itmax     =maximum number of iterations 
 zmin      =minimum depth to include 
 zmax      =maximum depth to include
 
 EXAMPLE OUTPUT SAMPLE FROM *.lst
  Iteration        LSQE        V1        V2        V3        Z1        Z2

         0      0.02201     107.5     206.7     305.8       4.8       3.8
         1      0.01985     108.6     221.8     316.6       4.7       3.9
         2      0.01791     109.7     238.5     327.0       4.7       4.0
         3      0.01616     110.6     253.2     337.0       4.6       4.1
         4      0.01458     111.3     269.3     346.4       4.5       4.2
         5      0.01202     112.0     285.5     355.4       4.5       2.0
         6      0.01087     112.6     314.0     364.2       4.5       2.0
         7      0.00984     113.1     345.0     372.6       4.5       2.0
         8      0.00891     113.5     379.0     380.5       4.5       2.0
         9      0.00807     113.9     416.9     388.0       4.5       2.0
        10      0.00732     114.3     459.7     395.1       4.5       2.0

The values Z1 and Z2 are layer thicknesses. So for iteration 10, the first layer is 4.5 meters thick. The second layer is 2 meters thick, placing the top of the half space at 6.5 meters depth.

Figure 27: BVSP: Solution is a first layer, 4.5 meter thick Vs=114.3 m/s, second layer 2.0 meter thick, Vs=459.7 m/s, on top of a half-space with Vs=395.1 m/s.
\includegraphics[scale=0.6]{Figure25.pdf}