Hi All. I have always thought that the New Idria thrust fault was an inactive fault. Now ever that may not be the case as the following quakes have been identified as occurring in the area of New Idria. These quakes occurred about 10 miles SE of New Idria on 10/25/1982. The fault map I have does show a number of faults in that area as well as other areas surrounding New Idria. However the faults are not named.

1982/10/25 22:26:03.61 36.3198 -120.5090 12.27 5.40 MLm
1982/10/25 23:12:16.82 36.3293 -120.5125 6.65 4.20 MLm
1982/10/25 23:15:53.95 36.3282 -120.5180 12.05 4.00 MLm
1982/10/29 00:52:10:48 36.3370 –120.5175 11.47 3.00 MLm ;
The following is the Coalinga quake of 1983. Using a radius of 10 miles so as to exclude most of the aftershocks from the Coalinga quake I found that a 137, M>3.0 and large quakes since 07/14/1970 have occurred within 10 miles of the 10/25/1982 5.4Ml quake although more then half of them are still in the aftershock zone of the 1983 Coalinga quake.

1983/05/02 23:42:38.13 36.2277 -120.3183 10.03 6.70 MLm

There were 3 quakes of M>4.0 to M>4.9 about 15 miles north of the Coalinga quake and about 12 miles east of New Idria, but they are clearly located on the Great Valley thrust fault. These quakes occurred in August of 1975.

The quakes of 10/25/1982 occurred about 10 miles NW of the Coalinga quake. Could these quakes have been foreshocks as well as the ones in August of 1975? There is no real way of telling if this is the case, but the quakes of 10/25/1982 were a fairly clear indication that something was building. As to where, there was no way of knowing.

With this in mind I have to wonder about the quakes at Bolinas, Bennett Valley, Yountville and Santa Rosa and how they relate to the Rodgers Creek fault most particularly the section of the fault from Rohnert Park to San Pablo Bay. Could there be other faults in the Bay Area where the stress is close to breaking? Sure wish I knew. Take Care…Don in creepy town

The quake data was gathered from the Northern California Earthquake Catalog and
http://quake.wr.usgs.gov/research/deformation/modeling/papers/CoalingaJGR2001.html