Noise, Not Signals

Claims made in your article "Earthquake Alarm" [December] that electromagnetic (EM) observations are earthquake predictors should be rejected.

Such claims all suffer from the same problem: natural EM signals in the earth and atmosphere due, for example, to solar activity and lightning, are ubiquitous. So are EM signals caused by human activity in industrial facilities and electric power plants; EM signals are also caused by radio and radar transmission.

Before arguing that EM signals are earthquake predictors, all known artificial and natural causes of such signals should be eliminated and a statistical correlation in excess of random chance should be demonstrated. Unfortunately, proponents of EM predictors have never done this. Carefully vetting their claims is hard work, but when such claims have attracted enough attention to justify independent evaluation, the EM observations have been shown to be either of artificial origin or artifacts of solar-terrestrial origin, with no relation to the earthquake.

Robert J. Geller, Alex I. Braginski, & Wallace H. Campbell

Geller is a researcher in seismology at the University of Tokyo; IEEE Senior Member Braginski is active in SQUID magnetometer research and applications; Campbell is a researcher in geomagnetism. An unabridged version of this letter is available in "And More Forum..." on Spectrum Online at http://www.spectrum.ieee.org.

The authors respond: Geller, Braginski, and Campbell are correct that electromagnetic signals associated with earthquakes must be discriminated against a background of natural and man-made noise. However, noise identification today is routine. We routinely identify periods of high solar noise and investigate relevant human EM noise before we begin to identify anomalous signatures. We also identify and eliminate "normal" magnetospheric signatures observed over years of monitoring.

DEMETER satellite data have yielded more than 3000 EM signatures around quakes of greater than magnitude 5, with statistically significant patterns. And infrared anomalies in 10 to 20 cases have been compared to background data to identify true earthquake anomalies. Ever more sensitive ground instruments and better space instruments have increased the validity of the EM signal data set.

Even with these data, and significant new lab results, EM/earthquake analysis is in its infancy; much is yet to be done to obtain a clearer picture of these phenomena.

Tom Bleier

Palo Alto, Calif.

Friedemann Freund

Mountain View, Calif.

My Dream Job

I made up my own dream job after I quit a boring application engineering job and set out full time to follow my interests and design a new breed of Class D audio amplifier ["More Fun at Work," February].

Less than a year later, I introduced it at the Consumer Electronics Show in Las Vegas; in 2005 my amplifier received rave reviews and won a few industry awards. Now I get to listen in the lab to the best music reproduction all day long from my own amplifiers, while I work on the next big thing at my own pace. My company, NPhysics, is growing fast. And the feedback I get from customers brings a lot of psychic satisfaction, besides the financial rewards.

Tran Nguyen

IEEE Member

Rohnert Park, Calif.

Due Credit

I am involved with the Sony PlayStation Portable (PSP) home-brew scene, and I was delighted to read your article on the subject ["Beating Sony at Its Own Game," February]. However, the article credits SonyXteam with releasing the 2.0 to 1.5 firmware downgrader that permits home-brew software to run on the PSP. It might be true that Sony released a firmware downgrader; however, MPH [another team of PSP enthusiasts] released the downgrader first and deserves credit for its breakthrough.

Ryan Haines

Ithaca, N.Y.

Author David Kushner responds: We didn't mean to imply that there is only one downgrader available for the PSP. Thanks for pointing out that many people are working passionately in this space.

Longer Life

While having a laptop run for 8 hours (with everything shut down, no doubt) might be nice [You Tell Us, "The 8-hour Laptop," January], wouldn't it be a better use of research dollars to develop a battery that would last more than a year or so in that laptop? I'd rather plug into a charger a little more often than shell out US $150 every year for a new battery pack.

Randy Warner

San Diego