Hello,

Not sure why this is happening, but it does not look random. Here is the PDE circular for the La Jolla quake, 30 Km, 3.5 mag and up. Ofcourse, this is only 34 years of data.

NEIC: Earthquake Search Results

U. S. G E O L O G I C A L S U R V E Y
E A R T H Q U A K E D A T A B A S E

FILE CREATED: Tue Sep 4 17:02:53 2007
Circle Search Earthquakes= 9
Circle Center Point Latitude: 32.767N Longitude: 117.340W
Radius: 30.000 km
Catalog Used: PDE
Magnitude Range: 3.5 - 10.0
Data Selection: Historical & Preliminary Data

CAT YEAR MO DA ORIG TIME LAT LONG DEP MAGNITUDE IEFM DTSVNWG DIST
NFPO km
TFS

PDE 1983 06 29 080836.40 32.63 -117.38 5 4.60 MLPAS 6D . ....... 15
PDE 1985 06 18 001255 32.68 -117.15 6 3.90 MLPAS 5F . ....... 20
PDE 1985 06 18 032228.60 32.68 -117.15 6 4.00 MLPAS 5F . ....... 20
PDE 1985 06 18 042814.80 32.67 -117.17 6 3.80 MLPAS 4F . ....... 19
PDE 1986 08 09 005230 32.60 -117.25 6 3.60 MLPAS 3F . ....... 20
PDE 1986 08 28 101418 32.58 -117.31 5 3.70 MLPAS 5F . ....... 20
PDE 1986 10 29 023815.30 32.61 -117.15 15 4.40 MLBRK 5F . ....... 24
PDE 2005 05 29 183045.70 32.57 -117.53 6 3.80 MLPAS 2F . ....... 28
PDE-W 2006 05 09 001336 32.63 -117.32 13 3.60 MLPAS .F . ....... 15