Homemade Seismometer for Earthquake Recording

This project describes how a seismometer is sensitive enough to detect and record earthquakes by constructing it using readily available parts with accurate time marker ticks.

The pickup coil generates the electrical seismic signal and is attached to the pendulum of seismometer within 1cm of the magnet. With respect to the pendulum and magnet, the movement of the seismometer’s frame and base is caused by the seismic disturbances. The amplitude of the resultant signal is in the low microvolt region since the motion is quite small and very slow and not visually perceptible. This weak signal is vulnerable to electrical interference and noise which will be amplified and filtered being used to drive a chart recorder.

Some form of filtering is required whenever the output of a given seismometer is subject to noise. The remaining of the noise is a true earth motion and not electrical in nature. It can be caused by manmade, local disturbances such as building vibrations from nearby machinery. They have a periodicity different from those of the earthquake waveforms. A more elaborate approach is required when filtering out the signals resulting from nearby disturbances without degrading the waveforms.