Short-Range Predictions
The goal of short-Range earthquake prediction is to provide a warning of the location and magnitude of a large earthquake within a narrow time frame. Substantial efforts to achieve this objective have been attempted in Japan, the United States, China, and Russia-countries where earthquake risks are high. This research has concentrated on monitoring possible precursors-events or changes that precede a forthcoming earthquake and thus may provide a warning. In California, for example, seismologists are monitoring changes in ground elevation and variations in strain levels near active faults. Other researchers are measuring changes in groundwater levels, while still others are trying to predict earthquakes based on an increase in the frequency of foreshocks that precede some, but not all, earthquakes.