Look at geologic maps to find the locations of past earthquakes. Maps showing the locations of past earthquakes are available from the United States Geological Survey (USGS). By looking at these maps, you can see where earthquakes may be likely to occur again based on where they have occurred in the past.Obtain information on when earthquakes have occurred in the past. In some locations that have experienced multiple earthquakes in the past, there may be some periodicity or pattern to when those earthquakes occurred. Knowing this periodicity can help you forecast when an earthquake may occur in the future. The USGS also has information on when earthquakes have occurred.
Examine seismograms, tracings or recordings of seismic activity at a particular location. If you see an increase in seismic activity on a seismogram, a large earthquake may soon follow.
Observe rocks in various areas. Sometimes, rocks will contain layers of disturbed sediments that indicate ancient, severe earthquakes. Knowing the locations of these past severe earthquakes can indicate that future severe earthquakes may occur in these same areas.
Take note of foreshocks. Sometimes large earthquakes are preceeded by smaller earthquakes known as foreshocks. If small earthquakes are occuring in a particular area over a particular period of time, then a larger, more severe earthquake may be forecasted for that area.
Look at the behavior of animals. Although highly controversial, some animals, such as dogs and cats, may change their behavior patterns prior to an earthquake.
Think about tidal forces. Tidal forces as predictors of future earthquakes is an unproven theory. The phenomenon, known as syzygy, says that tidal patterns can be used to forecast earthquakes, especially those involving oceanic crust.