zmap a tool for analyses of seismicity patterns typical applications ...

Figure 4.2: b-value maps of southern California for the period 1981-1992.42. (a) Maximum likelihood
method, (b) weighted least squares method.
The default scale for the b-values, with which the maps are presented, includes the
minimum and the maximum values that are found. However, it is usually better to select
limits that result in a map in which the blue and red are balanced. This is done by
selecting Fix color (z) scale from the Display menu in the b-value map window.
The first item of business when viewing a b-value map, is to check if the results can be
trusted. For this, one can click on any location of interest and view the FMD plot. For
example, the distribution at a location of high b-values is compared to that at a location of
low ones in Figure 4.3a. This plot was obtained by first selecting Select EQ in Circle
and then Select EQ in Circle overlay existing Plot from the Select menu in the b-value
map window. According to the Utsu test, the two distributions are different at a
significance level of 99% (p=0.1 in the top right corner).
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