The recovery and digitization of analog seismograms is critical for research into historical seismological events. Analog seismogram digitization is a difficult and complex problem and requires standards to successfully recover information from the analog media. This study investigates proposed standards for the digitization of analog seismograms. For this investigation, 'white noise' synthetic seismograms were used, with known frequency content that emulates analog records. The synthetic signal was modified to test variables such as scan resolution, interpolation algorithms, amplitude, line thickness, etc. After digitization, the digital seismograms were compared back to the original synthetic seismogram. Effectiveness of scan density can be quantified by the simplicity of digitization and waveform accuracy. Low scan resolutions adversely affect waveform accuracy and ultimately the frequency recovery. For example, a 200 DPI image can recover signals up to 2.5 Hz whereas a 600 DPI image can recover up to about 8 HZ, assuming an original recording speed of 60 mm/minute. Variability of the waveform thickness can change due to the focus of the recording beam/pen. Wider signal traces reduce the probability of accurately recovering high frequency signals due to hidden signals in the overlapping traces. We also observed the recoverable signal from low amplitude analog traces. Signals that exceed five times the width of the analog trace can be recovered within 3db of the true reference amplitude.
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