People have been predicting earthquakes by watching natural phenomena for thousands of years. Accurate predictions, however, could only be made by people highly sensitive to their natural surroundings.
Prior to an earthquake, the water level in wells or ponds sometimes changes, as does the amount of turbulence and the temperature in the water. Animals may act strangely before an earthquake. Land may rise several inches (centimeters) over time before an earthquake. Knowing the history of earthquakes in the area adds to predictability, because quakes generally follow a pattern.
Some scientists believe that earthquakes can be predicted as accurately as the weather. Nowadays, scientific instruments can measure changes in the electrical currents of Earth; the volume of rock near a fault; the level of water and land; the amount of radon gas escaping from Earth; Earth’s magnetic field; and the mounting stress within rock—all factors in predicting earthquakes.
Many countries, particularly Russia, Japan, and the United States, have accelerated their research into earthquake prediction in this century.
The number of faults under scientific observation, however, is a small fraction of the tens of thousands of miles (kilometers) of land prone to earthquakes.