Most predictions are based on attempts to determine a stress increase prior to rock rupture. This may involve geodetic measurements to monitor relative motions, changing elevation, etc., or phenomena resulting from stress accumulation (changes in the magnetization, temperature, gas release, etc.), some of which may affect animals. So far, most methods indicate only an increasing probability of seismic activity and cannot be used to predict an actual occurrence, other than the use of foreshocks, often only minutes prior to a major main earthquake, but such small earthquakes do not necessarily lead to major activity. Quiescence within an active seismic area can indicate either a gradual increase in stress or that stress release is taking place gradually. See focal mechanism; and earthquake magnitude.
Subjects: Ecology and Conservation — Earth Sciences and Geography.