A response spectrum is a term from dynamics. It is a diagram describing the response of a single-mass oscillator or several single-mass oscillators to vibration excitation.
A structural system is damped and the excitation occurs on a support node. An answer or a reaction to this vibration can be acceleration, a velocity, or displacement.
Response spectra are used in seismic design, for example, according to EN 1998‑1, and are derived and simplified records of the occurred earthquakes. It is then possible to analyze the reaction of the structure to such a response spectrum by means of the modal analysis, for example.
