Back in the mid 1960's, when I was in my mid 20's, I was an Engineering Tech with the department of water resources, I had the job of analyzing crustal strain measurements across the San Andreas Fault. The data were annual measurements with a Geodimeter of the distance between mountain tops, such as Mt. Hamilton to Loma Prieta (30 Km) and down to Palm Springs. The basic accuracy was better than 1 part/million, or about a cm on a 20 Km line, plus the onerous temperature error, 1 part/million/deg C. One of the staff programers wrote me a little program that looked for anything unusual, based on the expected value and the historical error on a particular line. This program, running on an IBM 1620, would print out "EARTHQUAKE COMING" on the data tabulation for any particular line. I kept a chart on my wall of predicted earthquakes, and hit on about three of them. Remember, we're predicting earthquakes in California with data taken once a year, so statistics were on my side. Our group manager read the chart, and perhaps having too much confidence in a young kid, announced one of the predictions at the AGU meeting. It made a good sized article in the San Francisco Chronicle. As you would expect, that particular earthquake didn't happen. Of course you don't get fired when you work for the government, but the Department of Water Resources eliminated his position from the budget next year and he went on to other things. The Geodimeter program was later taken on by the USGS, and they still do a lot of Geodimeter work, but they haven't found anything significant. I personally thought our problem was the long sample (one year typical) between measurements, so you had to be lucky to catch an earthquake. Back then of course, only sooth sayers predicted earthquakes. It was some years before the USGS decided that prediction was politically correct and fell on their face at Parkfield. Interestingly enough, I did have a pretty solid prediction of an earlier earthquake near Loma Prieta (the 196? Corralitos Earthquake), where the mountain actually bumped over about 10 cm from its expected position a short time before the earthquake. If you examine the USGS data for Loma Prieta, prior to the 1989 earthquake, you can see a similar pulse in the data. My program would have flagged the 1989 Loma Prieta Earthquake prior to the event. The USGS used a different prediction criteria and they reported "no prediction" even though it is obvious in the data. By the way, we did Parkfield before Parkfield was cool. The data said that the fault was just ripping along North of Parkfield, and locked up just South. We created and measured a large pentagon of Geodimeter lines in the area of interest before the Parkfield earthquake, and then came back and measured it again after the Parkfield earthquake, so you could say we predicted that one too and backed it up with some effort. It was all written up in a DWR Bulletin, but it was never referenced much because our leader was so discredited by his failed prediction. I wrote the report though, and it's good solid information on fault movement in California for that 10-year period. -- Doug Crice http://www.georadar.com 19623 Via Escuela Drive phone 408-867-3792 Saratoga, California 95070 USA fax 408-867-4900 __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>