OK, I promised a SCEC meeting post. Actually, I read the article on the plane on the way to the SCEC meeting, and then later at the Meeting heard Ray Weldon give his talk. The link below is (if it works) to the GSA Today paper by Weldon et al.....I recommend this to those with a science interest....Don, Canie, Roger...anyone else who want to focus on this. When I took seismotectonics class from Rick Sibson 15 years ago we studied time predictable and slip predictable earthquakes.

Time predictable is where two blocks at depth are sliding past each other at a constant rate (for example, 3 cm/yr).....if the previous earthquake slipped, for example, 3 m, the next earthquake will occur when 3 m of slip has accumulated....100 years.

Slip predictable says that for blocks slipping at 3 cm/yr, the longer it has been since the last earthquake, the larger will be the next one.

Weldon's group has developed a near-complete record of earthquakes on the San Andreas fault near Wrightwood. They have found that the data do not support either model. In fact, they support more the opposite. Most surprising, they show that for stretches of a few hundred years, the San Andreas fault slipped at 3 times the plate motion rate.

Another talk by Mike Oskins, and talk by Tom Rockwell last year, show that the GPS rate for the eastern California Shear zone is several times faster than the geologic rate for the least few hundred thousand years, or 10,000 years, respectively.

So, there is a lot of talk at SCEC about strain transients...where blocks move past each other faster for some period of time and then slow back down. I don't know how this works and I don't think anyone else does. And/or, when an earthquake occurs, it may not release all the stored elastic strain....which goes against a lot of data......

I have said on this site before that I thought the probabilities for earthquakes on segments of the San Andreas fault were underestimated for segments with low official probabilities, and overestimated for those with high probabilities...because, I thought that the fault might not beheave as expected. I was just unable to find on the internet the probability for the northern segment of the San Andreas fault or for Czrrizo plain segment...so I guess I better not comment.....I did find the study from a couple years ago on bay area probability, and the probablity for large quake on the San Andreas fault near San Francisco seemed reasonable....although I do not do this sort of analysis....

So....does anyone know the latest official conditional probability for large earthquakes on segments of San Andreas fault for 30 years from the date of the report, and can they link to it here?
Chris

• Weldon articlle