A little clarification; a seismometer is a sensing device. It's attached to amplifiers and ultimately a recording device, typically a hot pen recorder which melts thru the white wax coating on the black paper of the record, which is called the seismogram. Or alternately oit may deflect a light beam which is aimed at a piece of photographic paper, producing a black line on white paper.

Or in this day and age, the seismometer's output may go directly into a computer which analyses the signal and locates the quake.

Roger