,------------------------------------.

It is tempting to try to introduce a relationship between the modified Mercalli (MM) intensity and the maximum acceleration experienced at a site. Unfortunately, the correlation is rather poor, and for any particular MM intensity the acceleration tends to extend over an order of magnitude or more. The mean of the relationship is

log a = 0.25IMM + 0.25 (5.49)

where a is in cm/s2 and IMM is the modified Mercalli intensity. Thus for MM VIII scale, the predicted value would be 18% g whilst measurements of acceleration have ranged from 8 to 70% g.