Hi All. Everyone talks about the San Andreas Fault the Hayward Fault and a few of the others as a possible candidate for a large quake. There is another fault that has the potential of having a large damaging quake depending upon where it centered. It’s the Great Valley thrust fault. There has been quite a bit of activity along the whole section of the fault this year. More then what I have seen in the past. This fault is also responsible for the Coalinga quake in 1983.

This fault is not that far removed from the San Andreas Fault. The distance is around 15 miles east of the San Andreas. The fault has been broken into 14 segments. The total length of the fault is 299.375 miles long. Its highly unlikely that the whole fault could, or would go at one time, but if two segments were to go at one time the quake could be a fairly large one. Some of the longer segments could also generate a large quake.

The upper plate of the Coast Range thrust, consisting of Great Valley sequence with Coast Range ophiolite at a the base, is cut by the San Andreas fault only along the west side of the Diablo Range in central California. The Great Valley Thrust Fault is on the eastern side of the Diablo Range in the San Joaquin Valley. There the upper plate of the Coast Range thrust forms a broad blanket over the Franciscan rocks except in several places along the length of the Diablo Range where windows, or piercement structures, in the upper plate expose Franciscan rocks of the lower plate at Mount Diablo, Pacheco Pass, New Idria, and Park-field.

Having spent considerable time in South County or the New Idria area I can tell you the land shows every indication of having been tortured for millions of years. You can see where once there was a lake that had a nice smooth bottom, but is now turned up 90 degrees. The slate that can be seen in what is now a hill indicates this. There is a sulfur spring not to far from this location and further down the road is the Mercy Hot Springs. Further south is Griswald Canyon. I have been told that Griswald Canyon is volcanic material and was formed under the ocean. The best discreption I can give of it (which I’m sure you ladies are familiar with) is that is looks like giant pot scrubbers. The heavy-duty kind for cleaning off cooking oil and grease that has been baked on to the pans by the husbands barbecuing. It is pocked mark with holes ranging from the size in which you can put your hand in to the size in which you can sit in to some a little larger. All through this area you can see evidence where rocks have been subjected to great heat caused by compression have folded instead of breaking. Up on top of some of the ridges in the area there is basalt. For those not familiar with basalt it is volcanic rock. It is dark gray to black in color and most of it will have small pockmarks or holes in it.

Every time I see this it tells me that there has been earthquakes in this area that would rival the biggest ones around. This in turn makes me wonder if we could have another one in the future. Maybe it should be when are we going to have another one. The area that I’m looking at is between Coalinga and Bakersfield. That is the area that has had the greatest amount of activity this past year. It could be just a matter of time before there is another one. Take Care…Don in creepy town.