Hi Todd. I wish you wouldn’t ask these kinds of questions. They get me to thinking and that in turn gives me a headache.

Using the NEIC catalog which isn’t the best I started with quakes with a magnitude of M>5.0. I used a 150 mile radius with the center at 34.265N/116.758W. There were a number of M>5.0s (79 with some clearly aftershocks to a larger quake) scattered all over the place, but then I noticed something else. There appeared to be a loose pattern to quakes of M>6.0 and larger starting with a 7.0Ml in Baja, California just across the border in 1979 and ending with the Hector Mine quake in 1999.

Some of the quakes are clearly aftershocks and there appears to be one foreshock above 6.0Ml before the 7.6Ms in 1992. There also appears to have been 5 foreshocks of 5.0Ml+ before the quake in Baja. There doesn’t appear to have been any clear cut foreshocks to the Northridge quake in 1994. There were a few 2.0Ml+ before the quake, but as those are a dime a dozen I don’t see anything there that would draw my attention to. In hindsight yes, but in no other way.

PDE 1979 10 15 231654.50 32.63 -115.33 12 --7.00 MLBRK
PDE 1979 10 16 065843.20 33.02 -115.58 5 ---6.10 MLBRK
PDE 1980 06 09 032818.90 32.22 -114.99 5 ---6.40 Ms GS
PDE 1981 04 26 120928.40 33.13 -115.65 6 ---6.30 MLBRK
PDE 1986 07 08 092044.50 34.00 -116.61 12--- 6.00 Ms GS
PDE 1987 10 01 144220 34.06 -118.08 10 ---6.10 MLBRK
PDE 1987 11 24 015414.51 33.08 -115.78 4--- 6.50 MLBRK
PDE 1987 11 24 131556.40 33.01 -115.84 2--- 6.70 MLBRK
PDE 1990 02 28 234336.60 34.14 -117.70 5 ---6.20 MLBRK
PDE 1992 04 23 045023.22 33.96 -116.32 12-- 6.30 Ms GS
PDE 1992 06 28 115734.12 34.20 -116.44 1 ---7.60 Ms GS
PDE 1992 06 28 150530.70 34.20 -116.83 5--- 6.70 Ms GS
PDE 1994 01 17 123055.39 34.21 -118.54 18--- 6.80 Ms GS
PDE 1995 09 20 232736.27 35.76 -117.64 5--- 6.10 MLBRK
PDE 1999 10 16 094644.13 34.59 -116.27 0--- 7.40 Ms GS

As you can see the quakes have been gradually moving north and a little to the west.

Of course in the middle of all of this the Bay Area in Northern California was also having its share of quakes in the 5.0Ml+ to the 7.0Ml+ range.

It’s interesting what one can find in the quake catalogs. It’s even more interesting to see if one can make sense out it. Take Care…Don in creepy town