Hi all;

To answer to Chris' question I searched the ANSS
catalog for quakes from 1900-2008, mag 3 or larger
in a box form 40N to 27N and from 112W to 124W

Then I counted quakes per degree of latitude to
get a feel for where quakes happen.

Finally I took each 5.5 or larger as a main quake
if it was at lat 33 or less and counted the quakes
within 20 days of the main quake regardless of where
they were.

I expected a match between column 2 and column 3
but it's not quite that simple. Note the differences
particularly at 36 and 37 degrees.

40____2___2
39_1042__28
38_1801__53
37_5024_374
36_5478_103
35_3013__64
34_5401_136
33_3923_785
32_3150_541
31__613__22
30__201___6
29__128__12
28___66___9
27___37___0

Roger