Magnitude and Intensity

The severity of an earthquake may be measured by its magnitude or its intensity. Charles Richter developed a scale in the 1930’s for measuring the magnitude of earthquakes. As the number of seismograph stations grew, new scales based on Richter’s idea were developed. What is called the moment magnitude scale, for example, measures the energy released at the source of the quake.

Of course, these scales do not always reveal the degree of damage inflicted by an earthquake. Consider an earthquake in northern Bolivia in June 1994, with a magnitude of 8.2, which reportedly killed only five people. Yet, the 1976 quake in Tangshan, China​—with the smaller 8.0 magnitude—​resulted in hundreds of thousands of deaths!

In contrast with magnitude, intensity registration shows the effects that an earthquake has upon people, structures, and the environment. This is a more descriptive measure of the severity of an earthquake in human terms. After all, tremors in themselves do not usually harm people. Instead, collapsing walls, rupturing gas or power lines, falling objects, and the like cause the most injuries and fatalities.