A seismograph is used to record earthquakes.
The Richter scale is one way of measuring the magnitude of an earthquake. It was developed at the California Institute of Technology in 1935. Although the Richter scale indicates how strong an earthquake was, it doesn't measure how much damage an earthquake caused.
The Richter Scale
Charles Richter developed the scale that now bears his name while working at the California Institute of Technology. The Richter scale measures the amount of energy released by an earthquake. Geologists compare measurements recorded in a number of locations to calculate the exact location and magnitude of the tremor.
How Does the Richter Scale Work?
The scale is logarithmic, which means with every whole-number increase on the scale, the energy release increases tenfold. In other words, an earthquake with a magnitude of 4.3 on the Richter scale releases 10 times more energy than a quake with a magnitude of 3.3.
How Common Are Earthquakes?
Microquakes, which measure 2.5 or less on the RIchter scale, can't usually be felt by humans and happen around 9,000 times each year. Quakes measuring 5.5 to 6.0 happen about twice a day somewhere on Earth. These quakes may cause slight damage to nearby buildings. Tremors in the 6.0 to 6.9 range may cause significant damage to buildings; they happen about 100 times each year. Quakes in the 7.0 to 7.9 range happen about twice a month. Earthquakes with the power to destroy cities, usually with a magnitude of 8.0 or more, happen once every five to 10 years.
Magnitude and Intensity
Although the Richter scale measures the magnitude of an earthquake, or how much energy is released, another scale is used to measure the intensity of a quake. "Intensity" is a term used by scientists to measure the damage that an earthquake causes. To measure the intensity of an earthquake, the U.S. Geological Survey uses the Modified Mercalli Intensity Scale, or MMIS. To evaluate an earthquake using the MMIS, the Geological Survey sends a survey form to all of the postal addresses in an earthquake-impacted area inquiring about the damage suffered and other effects of the quake.
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