The ‘Moment Magnitude Scale’ (Mw) is preferred over the Richter Scale for large earthquakes because:
The Richter scale “saturates” (fails to distinguish) between very large earthquakes (above 7.0) because it only measures peak wave amplitude. The Moment Magnitude Scale (Mw) measures the total energy by considering the fault area and the amount of slip, providing an accurate reading for even the largest “megaquakes.” ANSWER: (B) It does not ‘saturate’ for very high-magnitude events.
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For massive earthquakes, the fault might rupture over hundreds of kilometers for several minutes. A standard seismograph measuring just the highest wave peak (Richter) misses the total duration and scale of the energy release. Mw calculates “Seismic Moment,” which is the product of the rock’s rigidity, the area of the fault that broke and the distance the rocks moved. This makes Mw the scientific standard for modern seismology, as it accurately reflects the true physical size of a catastrophic event like the 9.5 magnitude Valdivia earthquake.