No. 100: Jul-Aug 1995
Some luminous phenomena accompanying the January 17, 1995, Kobe earthquake were mentioned in SF#99. Geomagnetic perturbations were also recorded:
"At Kyoto University's observatory in Mineyama, the terrestrial magnetism suddenly changed in a southeasterly direction by up to 0.6 nanotesla, for 30 seconds, as the quake began at 5:46 a.m. on Jan. 17.
"A similar geomagnetic variation was also observed at the university's observatory in Shigaraki, but the variation was in the opposite, north-westerly, direction."
(Anonymous; "Changes in Geomagnetic Field Noted during Quake," Daily Yomiuri, March 30, 1995. Cr. N. Masuya)
Comment. Such clear-cut, earthquake-associated geomagnetic perturbations are rare. For a short history of the controversy, see GQM1 in the catalog volume: Earthquakes, Tides, etc. (Details here.) Evidently, strong earth currents are created when rocks fracture and slip, but the precise mechanism remains obscure.