In recent years, seismologists have developed a new scale, called moment magnitude, that avoids many of these limitations. Moment is a physical quantity related to the total energy released in the earthquake. It can be estimated by geologists examining the geometry of a fault in the field or by seismologists analyzing a seismogram. Several recent earthquakes have confirmed that these two estimates agree. Because the units of moment are cumbersome, it has been converted to the more familiar magnitude scale for communication to the public.
Moment magnitude has many advantages over other magnitude scales.
First, because it looks at the total energy, we can measure all earthquakes, large and small, near and distant, with the same scale. Second, because it can be determined either instrumentally or from geology, we can use it to measure old earthquakes and compare them to instrumentally recorded events. Third, because it is more reliable, we can compare the size and energy of different earthquakes with more confidence, and better estimate what might happen in the future. For more information about earthquake science, read the following books . Click here for complete Bibliography.