Understanding the Earthquake Magnitude Scale

Understanding the earthquake magnitude scale can be a challenge. Exponential scales are not something we encounter often in daily life. The difference between a magnitude 6.0 and a magnitude 7.0 earthquake may not seem like much, but it represents a 33-fold increase in destructive power; and an 8.0 earthquake releases nearly 1,100 times more energy than a 6.0.

This two-minute video, produced by Living Planet, conveys just how quickly the potential damage grows along with seemingly minor changes in magnitude.

The moment magnitude scale represents how much energy was released during an earthquake, not how much shaking occurred. The amount of energy released indicates how much rock and earth moved, and how far. This is a more accurate measurement than the old Richter scale, which measured the amount of shaking recorded by seismographic needles (Note: shaking is still measured, now by the Modified Mercalli Intensity Scale).

While magnitude is important, it is not the only critical factor in determining how much damage occurs.  Where the earthquake strikes can be more important than magnitude. Deep thrust earthquakes, which occur miles below the surface, may have a large magnitude but not cause much damage because the energy and shaking dissipates before it arrives. Shallow crustal fault earthquakes tend not to spread very far but can produce intense, highly damaging shaking locally. And of course, earthquakes underneath the ocean can cause devastating tsunamis to coastal areas thousands of miles away.

For more information on preparing your organization for earthquakes, and any other type of emergency, contact AK Preparedness at info@akpreparedness.com.