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

Narrowing the target of investigation: At this point one might decide to study just the
shallow seismicity. Because of the minimum of the numbers at 35 km depth (Figure 5),
this offers itself as the natural cut. The bulk Mc for the shallow events can be estimated
by the same steps as outlined above. It turns out to be 1.9. Therefore, you may want to
map the Mc for the shallow seismicity with a catalog without the events below M1.5,
because we know that not enough parts of the catalog can be complete at that level. The
catalog for the period and area with depths shallower than 35 km and M>1.4 contains
15078 events. The map of Mc (Figure 9) is obtained by selecting Calculating Mc and b-
Figure 9: Map of magnitude of complete reporting.
value Map from the Mapping b-values menu in the ZTools menu of the seismicity map.
The cross hairs that appear are used to click by left mouse button the polygon apexes
desired, and terminating the process by clicking the right mouse button. Once the
computation is completed, you can save the resulting grid (which also contains the
catalog used) for reloading later on. Pressing Cancel will just move on without saving.
It might be fun to interpret the b-value map that is presented at first after the calculation,
but first we should examine the Mc map. We call for it by selecting mag of
completeness map in the menu of Maps in the seismicity window (Figure 9). Here the
symbols for the epicenters are selected as none, such that they do not interfere with the
information on Mc.). In it, we see that the offshore catalog is inferior since Mc>3.5.
Before we accept the Mc map, it is a good idea to sample a number of locations to see if
we agree with the algorithm’s choice of Mc by visual inspection of the FMD plots. For
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