Today's high-technology, digital seismographs record ground shaking over a large band of frequencies and seismic amplitudes. Today's seismometers are called broadband because they are able to sense ground motion over a wide range of frequencies, from thousands of seconds to less than a hundredth of a second.

The amplitude of the signals recorded by old seismometers was limited by the amount of movement possible between the mass, or pendulum, and the seismometer housing. Today's seismometers operate by measuring the amount of electrical energy needed to keep the mass centered in the housing in the presence of strong ground shaking. Modern seismometers can record a wide range of seismic signals, both very small and very large.