Isolation from seismic motion can be realized by the use of mechanical filters with elastic components, such as springs and suspension wires. As the simplest example, consider a one-dimensional harmonic oscillator shown in figure 2.3. The oscillator consists of a spring with a spring constant k and a suspended payload with mass M. The displacements of the suspension point and the payload are denoted as x 0 and x respectively. The equation of motion of this system is written as