Hi all;

At the suggestion of Dr Alan Jones I have revised the text as follows:

1) Select the time span of interest.

2) Divide the time span into consecutive windows of the predicted length

3) Compute the total number of windows in the time span

4) Count the number of windows containing one or more quakes

5) Divide the number of windows containing quakes by the total number of windows. The answer is the probability that such a window will contain a quake.

The time span to be used is a matter of opinion. A long time span gives a long term average answer whereas a shorter time can better suit changing circumstances. Care must be taken that the time span does not exceed the catalog's reliable period inasmuch as network capability increases with time.

Roger