08/03/2023
Ever wondered how a seismometer works? A seismograph is a device for measuring the movement of the earth, and consists of a ground motion detection sensor called a seismometer, coupled with a recording system.
A simple seismometer that is sensitive to up-down motions of the earth can be understood by visualizing a weight hanging on a spring. The spring and weight are suspended from a frame that moves along with the earth’s surface. As the earth moves, the relative motion between the weight and the earth provides a measure of the vertical ground motion.
If a recording system is installed, such as a rotating drum attached to the frame, and a pen attached to the mass, this relative motion between the weight and earth can be recorded to produce a history of ground motion, called a seismogram.
Seismographs operate on the principle of inertia—stationary objects, such as the weight in the above picture, remain stationary unless a force is applied to them. The weight thus tends to remain stationary while the frame and drum are moving.
Modern research seismometers are electronic, and instead of using a pen and drum, the relative motion between the weight and the frame generates an electrical voltage that is recorded by a computer.
