ultra-low frequencies (ULF; frequencies less than 5 Hz),
extremely-low frequencies (ELF; frequencies in the range 5 Hz - 3 kHz), and
very-low frequencies (VLF; frequencies in the range 3 - 30 kHz).

Frank may be monitoring a ULF site - there are 6 ULF antennas in california that I know of - it takes a very large amount of land to set one up. Frank says he's using a Fluxgate Magnetometer which is something else entirely (as far as I can tell) - details on it at this site: http://xtrsystems.com/magnetometer/layout

Tony Fraser Smith is the person typically regarded as noticing odd ULF readings. He was measuring radio waves below 100 cycles per second when the Loma Prieta earthquake hit. Look at Thomas Tao-Ming Liu's link off the site below and you can get an idea of the size of the ULF array.

Ahh - here is a link for the existing antennas: http://www.seismo.berkeley.edu/seismo/bdsn/em.overview.html - i think the data may be available via this site. A little more reading/searching will be required.

Canie

• Antony C. Fraser-Smith