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Knowing the Risk
In accordance with the Richter scale, the magnitude of a seismic event is calculated using the logarithm of wave amplitude as recorded by seismographs, taking into account the distance from the location of the measurement to the location of the earthquake. The following equations are standard:

Moment = (rock rigidity) x (fault area) x (slip distance)
Mo = uAd

Mw = 2/3 (log10Mo - 16.0)

As a result of the logarithmic scale in combination with the rest of the equation, an integer increase in magnitude corresponds to an increase of 31.6 times the amount of energy released, not the expected 10 times increase.
Alternatively, earthquake magnitude can be reported according to the Modified Mercalli Scale, which is based upon observed effect.


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Designing the Structure
During the design process, the engineers of SWSE take into account such factors as: the proximity of the structure to the local fault zones; the type of soil on which the structure will rest; and the intended use of the building. Such critical structures as hospitals are designed with the greatest resilience to seismic forces. Data such as the maximum historical ground acceleration at the building site can be obtained using seismic maps from previous earthquakes.		  

A Visual Model
The Learning Channel's Make-A-Quake allows you to input building location, type of foundation, and earthquake magnitude, then provides a corresponding animation.