Can earthquakes be predicted? Scientists are working on programs to predict where and when an earthquake will occur. They hope to develop an early warning system to save lives. Scientists who do this work are called seismologists.
Earthquakes are the most dangerous and deadly of all natural events. They occur in many parts of the world. Giant earthquakes have been recorded in Iran, China, Guatemala, Chile, India, and Alaska. Two of the biggest earthquakes that were ever recorded took place in China and Alaska. These earthquakes measured about 8.5 on the 10 Richter Scale.
The Richter Scale was devised by Charles Richter in 1935 and is used for comparing the energy level of earthquakes. An earthquake that measures 2 on the scale can be felt, but causes little damage. One that measures 4.5 on the scale can cause slight damage, and an earthquake that has a reading of over 7 can cause major damage.
How do earthquakes occur? Earthquakes are caused by the movement of rocks along cracks, or faults, in the earth’s surface. The fault is produced when rocks near each other are pulled in different directions. The best-known fault in North America is the San Andreas fault in the state of California in the United States.
The nations that are actively involved in earthquake prediction programs include Japan, China, Russia, and the United States. These countries have set up stations in areas of their countries where earthquakes are known to occur. These stations are ready for warning signs that show the weakening of rock layers before an earthquake.
Many kinds of seismic instruments are used by these places to watch the movements of the earth’s surface. One of the instruments is a seismograph. It can follow vibrations in rock layers thousands of kilometers away. Tiltmeters are used to record surface movement 30 along fault lines. Seismologists use gravimeters to measure and record changes in local gravity. The scientists also check water in deep wells. They watch for changes in the water level and temperature, which are signs of movement along faults.
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