Large earthquakes may broadcast warnings, but is anyone tuning in to listen, asks Stanford researcher
Some seismologists are suspicious that these results are real, Fraser-Smith said. But it would take little effort to verify or disprove them. He is calling for federal funding for a mission-oriented study that would place approximately 30 of the ultra-low-frequency-detecting instruments around the world at hotspots for big quakes. It would cost around $3 million to buy 30 of these machines, he said, which is cheap compared to the cost of many other large studies.
Every year, there are on average 10 earthquakes of magnitude 7 or higher around the world. So within just a few years, he said, you could potentially have 10 new measurements of electromagnetic waves before big quakes！surely enough to determine whether the previous four findings were real.
Fraser-Smith will present his findings at the American Geophysical Union meeting this week in San Francisco. His talk is scheduled for 8:45 a.m. Thursday, Dec. 13.
Theory and Applications of Electromagnetic and Thermal Anomalies During Earthquakes II
The 1989 Ms 7.1 Loma Prieta, California, Magnetic Earthquake Precursor Revisited
*J N Thomas, J J Love, M J Johnston
Re-affirming the Magnetic Precursor to the 1989 Loma Prieta, CA, Earthquake Using Magnetic Field Data Collected in the US in 1989 and 1990
*D Culp, S Klemperer, J Glen, D K McPhee
Dec. 16, 2007
Link examined between quakes and magnetism
Scientists divided on whether spike in readings warned of Loma Prieta
By Betsy Mason, STAFF WRITER
InsideBayArea.com
Yes, this is an interesting article but..... journalist Betsy Mason who wrote it surely gave her best to present what the media call "a balanced view". What she missed was the fire underneath the cool and polite surface at the AGU session S41D.
At this AGU 2007 Fall Meeting I heard the USGS talk for a second time (the first time was at the EUGG meeting in Perugia, Italy, this past summer). The USGS team presented what effectively constituted an accusation that Tony Fraser-Smith and his group had manipulated the low frequency EM data recorded prior to and after the Oct. 1989 Loma Prieta earthquake in order to make them look the way they were published in 1990.
The USGS trio set out to show that magnetic storms could have caused the reported signals. The trio presented their case by inferring that, about two weeks before the earthquake, someone had tweaked the amplifier of the unattended ULF station located in the garden of a private house high up in the Santa Cruz mountains, 7 km from where the epicenter was going to lie. This tweaking led to a sudden increase in the baseline signal intensity. Then, 30 min before the earthquake, the same or another unknown person allegedly tweaked the amplifier again, giving the baseline signal another boost. After the earthquake and after the Stanford group had rushed to the site to restart the data acquisition after the power failure, somebody (again allegedly an unknown "bad boy or girl") tweaked the amplifier over several weeks, taking it down step by step for the signal to finally return to its normal baseline intensity.
For the next point to become clear it is important to note that, back in the late 1980s, the Stanford group had set up the data acquisition is such a way as to process the data on-site in 30 min intervals, discard the raw data and save the processed data on disk.
Magnetic storms coming from the sun are, of course, recorded all over the hemisphere. Hence, the USGS trio looked at solar storm data and found that, if the Stanford group did not process their data every 30 minutes but every 26.7 min, and if this error was introduced at a certain date, one obtains a fairly good fit of the pre-earthquake data with a few (rather weak) magnetic storms in the days before the Loma Prieta event. As to the post-earthquake data the USGS trio proposes a similar exercise involving shifting whole strings of data on the time axis to fit magnetic storms (this time rather strong).
What is not apparent from the journalistic "balanced" report is that, in my opinion, the USGS trio fell flat on their faces. In the presentation immediately following theirs, by a young Stanforder, a Stanford professor plus two young USGSers, just two powerful counterarguments were presented:
(1) ULF emissions coming from deep below are known to suffer severe attenuations as they travel through the rocks. As a result the lowest frequencies make it to the surface rather well, while the higher frequencies are increasingly attenuated. The Stanford station up in the Santa Cruz mountains recorded in 8 separate channels, each representing a certain frequency range. The signals in each channel suffered their characteristic attenuation, different from the attenuation of the neighboring channels. If some "bad boy or girl" had indeed tweaked the amplifiers, he or she would have had to do it a very specific way, different for each channel, and divinely prescient of the fact that the epicenter of the coming earthquake was going to lie exactly at a distance of 7 km and at a certain depth.
(2) If the Stanford group made the gregarious error of miscalculating their periodic processing time and used 26.7 min rather than 30 min, assuming that this mistake started at the beginning of the month when the earthquake occurred, the entire ULF record would be shifted toward earlier times. One of the consequences would have been that the last ULF spike before the earthquake and power failure, which led to an interruption of the record, occurred about 1 1/2 hours before actual earthquake time. In a tongue-in-the-cheek way the presenters of this rebuttal reported that the owners of the house in whose garden the Stanford station was installed don't remember that their electric power failed 1 1/2 hours before the Loma Prieta shock.
Sometimes "balanced" journalistic reports like the one by Betsy Mason for Inside Bay Area News don't let the drama of real life (and real science) shine through.
