Damage Level versus Shaking Severity Level

Legends on maps published as part of the original On Shaky Ground report in 1995 used damage level, ranging from "Pictures Move" to "Extreme Damage", to describe the various map colors (MMI levels). This damage level represents the estimated overall level of damage that will occur for various MMI levels. The damage, however, will not be uniform. Some buildings will experience substantially more damage than this overall level, and others will experience substantially less damage.

Legends on current maps instead use shaking severity level, ranging from "Light" to "Very Violent".

The change to the legend was made in order to emphasize the fact that not all buildings perform identically in an earthquake. The age, material type, method of construction, size, and shape of a building all affect its performance. In addition, structural mitigation measures make a large difference.

Maps published in 1995 are still current. Only the descriptions in the legend have changed. The maps themselves (shape, colors, and MMI values) have not changed.

Shaking Hazard Maps page