The figure below is from the upcoming lab. The horizontal axis is the structure's period, and the vertical axis is its maximum response during the shaking This spectrum shows the spring force response for a particular oscillator, but it is also possible to plot acceleration, displacement, and other response quantities. The spectrum indicates which buildings the earthquake will affect most. For this earthquake, resonance effects are most significant for structures with a period of less than 0.7 seconds. The spectrum indicates shows the 'color' of the earthquake.
Most earthquakes are violet, with most of their energy in the short-period range.
Some are more red, with lots of long-period content. Prediction requires wind tunnel testing The acceleration response of the building depends on the behavior of turbulent flow, which has no good mathematical models. In addition to perceiving general changes in velocity, the body is particularly sensitive to changes in velocity that result from vibration. The human body is a structure Body parts have mass and stiffness, and hence natural periods of vibration. These parts can resonate with a forcing function, and become highly perceptible and annoying.