Normal electromagnetic variations, tectono-magnetic effects, earthquakes, and animal behavior

The temporal and spatial variations of the geomagnetic field at the earth's surface can be as much as 100 gammas/minute and 200 gammas/km, respectively. Tectono-magnetic signals from the most likely physical, mechanisms are expected not to exceed a few gammas. Observations along the San Andreas fault of earthquake related tectonomagnetic signals indicate maximum signals of less than four gammas, while similar observations on active volcanoes indicate a few tens of gammas. An explanation of the origin of anomalous animal behavior in terms of a magnetic source implies either a capability to discriminate against the temporal and spatial field variations or the existence of some as yet unknown and unobserved localized source with larger anomaly amplitudes.