The movies color the landscape in each frame according to the maximum (peak) intensity of shaking (amplitude of the ground motion) up to that point in time. The color scale is the same as the one used in ShakeMap. In order to show the intensity of the current shaking, the colors darken as the shaking intensifies. At some locations, the most intense shaking lasts for several seconds, so the colors will darken as seismic waves continue to cause strong shaking. The first example shows how the colors change as the shaking at a location progresses from no shaking through weak, moderate, and strong shaking, peaking at a violent shaking level (very dark red), before the shaking dies off (red becomes brighter). The second example shows the color progression for a location that peaks at a strong level of shaking.
Shaking Intensity
- MMI II-III (blue)
- weakly felt
- no damage
- usually P wave in large event
- MMI VII (orange)
- perception of severe shaking
- potentially moderate damage to modern structures.
- often S wave in large event
- MMI X (dark red)
- extreme shaking
- potentially very heavy damage to structures