Howdy Roger,

What I have been looking for is a change of depth of the micro activity at Anza prior to a larger quake---4.5 to 5.2. I did a search of 4.5+ quakes centered at 33.600N, -116.600W, (40 Km) and found 7 quakes which fit the bill.
Below; (Credit to USGS)

FILE CREATED: Thu Aug 20 18:00:34 2009
Circle Search Earthquakes= 7
Circle Center Point Latitude: 33.600N Longitude: 116.600W
Radius: 40.000 km
Catalog Used: PDE
Magnitude Range: 4.5 - 9.9
Data Selection: Historical & Preliminary Data

CAT YEAR MO DA ORIG TIME LAT LONG DEP MAGNITUDE IEM DTSVNWG DIST
NFO km
TF

PDE 1975 08 02 001407.70 33.52 -116.55 13 4.7 MLPAS .F. ....... 10
PDE 1980 02 25 104738.70 33.52 -116.55 6 5.6 MLBRK 6D. ....... 10
PDE 1982 06 15 234921.30 33.55 -116.67 12 4.8 MLBRK 5F. ....... 8
PDE 1986 10 15 022847.70 33.95 -116.57 9 4.7 MLPAS 5F. ....... 38
PDE 1997 07 26 031455.99 33.40 -116.35 11 4.8 MLPAS 4F. ....... 31
PDE 2001 10 31 075616.63 33.51 -116.51 15 5.1 MLPAS 5F. ....... 12
PDE 2005 06 12 154146.54 33.53 -116.57 14 5.2 MwHRV 6DM ......S 8

So my question now is if you can do a 90 day periocity on the depths of micros before these quakes. It would be a small sample of the overall (400,000) listed quakes in ANSS catologue. Another problem with such a data set is to establish a nominal depth for all micros so a differentiation can be found, if such a condition exists. I don't care about aftershocks.

My guess is that the program would have to be capable of doing a mathematical summation of the depths, and then configure a root mean square of the data.

Possible???? Probing for comments...corrections.

Thanx,
Glen