I have just started to study resonance and I don't quite understand what it is. My textbook says: "All objects vibrate with a characteristic "natural frequency". When an object is forced to vibrate at its natural frequency, the amplitude of its vibration can grow very large. This effect is called resonance." This seems to be saying that all objects are constantly vibrating. Is that true? It then goes on to say: "The seismic waves from an eathquake force the buildings on the sufrace to vibrate. If the frequency of the vibrations is at the natural frequency of the building, then the amplitude of the vibration increases. More energy is transferred to the building and the building will probably fall down." Does that mean that the building was vibrating before the earthquake struck, and then the earthquake induced further vibrations onto it which doubled the intensity of its natural vibrations thereby forcing the building to come apart and collapse?