Hi All. I recently plotted all the aftershocks over M>3.0 and there appears to be two distinct locations for the aftershocks. One is east of the main event and the other is south of the main event. It sort of gives me the impression that the M>6.5 may have triggered a quake on the Oceanic fault which is close by which for all purpose and intent would be like an aftershock to the main event. At present time I have no way of knowing if this is the case or not.

From the Houston Chronicle.
“According to seismologist last week's magnitude 6.5 quake, seismic recording instruments showed it produced stronger shaking in the Paso Robles area than in San Simeon, near the epicenter, acting State Geologist Michael Reichle said.”

“The largest ground motion recorded was 50 percent of the force of gravity at a hospital in Templeton, on U.S. 101 between Paso Robles and Atascadero, he said.

Another instrument, on California 1 at the bridge over San Simeon Creek, just six miles southwest of the epicenter, showed ground motion of 18 percent of gravity.”

“The U.S. Geological Survey's Internet site showed that the apex of scores of aftershocks Monday night and Tuesday morning was pointed directly at Atascadero, where at least one home slid off its foundation and ended up at the bottom of a hill.”

“Paso Robles and Atascadero were outside, or in front of, the rupture zone, but the instrument readings did not necessarily mean they were shaken harder than the southeastern-most points in the zone, since there were no instruments there.”

The same thing was seen after the Loma Prieta quake. Morgan Hill and Gilroy, which are two towns closer to the epicenter of the quake, had some damage, but nothing compared to the damage that was seen in San Francisco and Santa Cruz that are further away. I know here in the Hollister area we hear the quakes south of us before we actually feel them. This occurs with almost all of the quakes in the upper M>3.0+. The sound is sort of a booming noise. 7 to15 miles from Hollister seems to be the limit for which we hear the quakes. If they are closer the quakes will be more to the west of us and the further south they are the less likely we would hear the noise. Not sure about a quake in the M>5.0+ range. I know I didn’t hear anything from the M>5.4 quake we had in August of 1998. Sure felt it though. Anyway quakes south of us will more often as not will be felt as a jolt while a quake near the same magnitude and distance to the north of us will be as a rolling motion.

As of right now no one is sure as to which fault caused the San Simeon quake. The most likely candidacies are the Nacimiento Fault, Oceanic Fault and the San Simeon-Hosgri Faults although I’m not sure about the San Simeon-Hosgri fault, as I have never seen it called that before. There is the San Simeon Fault and then there is the Hosgri fault, but the fault map I have shows no connection between the two. The San Simeon Fault is near the Hosgri Fault Zone so this could be the connection. In my opinion this fault is to far to the west to be the cause of the quake unless of course the quake isn’t properly located. Take Care…Don in creepy town

• San Simeon Quake