Physics
Seismograph: ground and inertia
An inertial mass records motion relative to shaking ground.
Try this
Compare a short wave packet with continuous shaking. Change the natural period and damping; displacement is magnified on the instrument.
The model and its limits
Single horizontal degree of freedom with prescribed ground acceleration. This is an instrument response, not an earthquake or regional propagation forecast.
Equations used in the module
Equations z″ + 2 ζ ω_0 z′ + ω_0² z = -y″ ω_0 = 2π / T_0
