What are Earthquake Magnitude and Intensity?
The severity of an earthquake can be expressed in terms of both magnitude and intensity. However, the two terms are quite different, and they are often confused. AMagnitude@ is related to the amount of seismic energy released at the epicenter of the earthquake. It is based on the amplitude of the earthquake waves recorded on instruments which have a common calibration. The most commonly used magnitude scale is the Richter Scale. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value. Although the Richter Scale has no upper limit, the largest known shocks have had magnitudes in the 8.8 to 8.9 range. AIntensity@ is based on the ob
