Seismogram

Today, practically all seismograms are recorded digitally to make analysis by computer easier.

Prior to the availability of digital processing of seismic data in the late 1970s, the records were done in a few different forms on different types of media.

A piece of paper is wrapped around a rotating drum of the helicorder which receives the seismic signal from a seismometer.

In the model that use ink, regular maintenance of the pen must be done for accurate recording.

[2] A Develocorder is a machine that records multi-channel seismic data into a 16 mm film.

[3] After the digital processing had been used, the archives of the seismograms were recorded on magnetic tapes.

The data from the magnetic tapes can then be read back to reconstruct the original waveforms.

Due to the deterioration of older magnetic tape medias, large number of waveforms from the archives in the early digital recording days are not recoverable.