PLOTPOLARITY takes the s-file name as input and makes a plot of P-wave
onset with polarity readings if available. The program provides an
efficient way to plot and change polarities used to determine
fault plane solution. Only vertical channels of data are shown.
If changes are done, the program will
save, if the user wants to, these back to the s-file.
The plots can extend over several pages
when there are many traces.
PLOTPOLARITY can be started from EEV using command 'pol', or from the command line using either, e.g.:
to plot traces which have polarities in s-file already, or with:
plotpolarity 09-2257-08L.S201508 all
to plot all vertical channel data. This is the default option when
starting the program from EEV.
The program asks for some input at the startup:
total window duration (default 1s): 2This is the total window duration that will be displayed around the P arrival, which is taken from the s-file.
P-onset position as percentage of total duration (10-90; def 50 = middle): 60
This number gives the position of the P arrival within the time window
as percentage of the total window. Setting this to 0 would mean that
the signal starts from the P arrival, 50 means that P will be in the
center of the window, and so on. Numbers less than 10 and greater than
90 will be reset to 10 and 90, respectively.
One typically wants enough pre-phase time to see how the signal is changing.
window length in seconds for averaging (default is 0)
This allows to average the samples for the given time period
starting the given length prior to the time of a sample. The
averaging will act as a filter without a phase response, and
can be looked at for noisy signals, best only to confirm if the
signal seen on original trace is still the same when applying averaging
Next the plot comes up, and the polarities can be inspected and changed, using keys c=compression, d=dilatation and r=remove. In case of a change, a message is written to the terminal, and the graphics are updated. For each trace, the station name is shown together with the the phase, the polarity (empty if not available), the distance and azimuth. The graphics are written to a Postscript file polarity.eps, an example is given in Figure 24.1.