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

Rough selection of the period of interest: It is evident from Figure 1.3a that only very
large events are reported before the mid 1960s. Because this is not the subject of your
quest and you want to concentrate on the small magnitude events, you delete all data
before the reporting increase in the 1980s by selecting Cuts in Time Cursor in the
ZTools button of the Cumulative Number window and clicking with the appearing
crosshairs at the beginning and end of the period you want. This re-plots the cumulative
Figure 1.3: Cumulative number of the selected earthquakes as a function of time.
number plot (Figure 1.3b) for a period during which the rate of earthquakes reported was
approximately constant with time. This suggests that the reporting may have been
homogeneous from 1989 on. Because this is the type of catalog you want, you now click
on Keep as newcat, which re-plots the epicenter map as seen in Figure 1.4.
Figure 1.4: Epicenters after rough selection of area and period.
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