Electric and magnetic fields — localized changes in magnetic and
electric fields (including changes in ULF, VLF, ELF and RF fields).
There is the uncontested observation of a localized strong ULF field
change that took place in the area of the 1989 Loma Prieta, California
earthquake (magnitude 7.1) during the hours prior to the main shock.
A weaker field change was observed about 2 weeks before the main
shock.