The 2015 Nepal earthquake magnitude of 7.9 was on which scale?

• A. Moment magnitude scale.
• B. Beaufort scale.
• C. Saffir-Simpson scale.
• D. Richter scale.

Answer: (D)

Measuring how much energy an earthquake releases is done with the moment magnitude scale. For large quakes like the Nepal event, scientists use Mw because it is based on seismic moment, which depends on the fault area that slipped, how much it slipped, and the rock’s rigidity. This gives a consistent estimate of energy release across big earthquakes, unlike older scales that can saturate and become unreliable for large events.

The other scales don’t fit here: the Beaufort scale measures wind force, not earthquakes; the Saffir-Simpson scale measures hurricane intensity; and the term often called the Richter scale is an older local magnitude measure that works well for small quakes nearby but underestimates larger ones. So the scale used for a magnitude around 7.9 is the moment magnitude scale.