23.8 Plotting fault plane solutions

There a many ways of plotting fault plane solutions in SEISAN: Through EEV (a single event), program FOC (many events), program PLOTFOC (single event without station information), program MOPAD which also can plot a moment tensor solution, program EPIMAP (many events), option MAPS in EEV (one event on a map) and W_EMAP (many events). The input file is in all cases a CAT-file. In addition, using program SEIGMT, a file to be used with GMT is prepared, however the use must make his own script. Only through EEV is it also possible to plot the observations.

Data can also be exported in GMT format with programs SEIGMT and MOPAD.

Using EEV
Command fo will plot all events in S-file. This can be a useful ways of comparing solutions obtained by different programs, see Figure 23.8. It is a requrement that the event can be located and polarities will be shown, not amplitudes. Command foo will work as fo but no polarities are shown. There is no requirement for the event to be located so foo can be used if an S-file only has a header line and fault plae solution(s).

Command fh will plot a moment tensor solution with MOPAD program.

Figure 23.8: Compare fault plane solutions from different programs. For explanation of symbols, see FOCMEC.

Using FOC
See under FOC for how to run the program.

The plot is seen in Figure 23.9.

Figure 23.9: Example of plotting many solutions. Each solution is given with number, the fault plane solution and the quality (A-E). Up to 24 solutions can be plotted on one page.

Using PLOTFOC The program asks for input of

W_EMAP (Windows only) plots the solutions as seen in Figure 23.10. In this case the simplest is to give command w_emap file, where file is the CAT file with fault plane solutions. See W_emap manual in INF. NOTE: Some versions of W_EMAP plots some of the fault plane solutions with inverted color e.g. inverse fault becomes a normal fault).

Figure 23.10: Plotting many fault plane solutions. Left: Using W_EMAP. Notice that the colors in the solutions are inverted compared to normal practice. Right: Using EPIMAP. The data for the two plots is the same.

The EPIMAP plot for the same events is shown in Figure 23.10. See EPIMAP for more explanation. EPIMAP can also plot the fault plane solutions in a section, the solutions are still seen in the horizontal plane.