The sampling process
Digital seismograms are sequences of numbers which in general have been obtained from the continuous output voltage of a seismic sensor by the procedures of sampling and analog to digital conversion. We will now consider some of the characteristic properties of these processes. We will simulate the sampling of analog data and its reconstruction from sampled values. We will find that an analog signal can only be reconstructed from its sampled values, if the frequency content of the signal to be sampled contains no energy at and above half of the sampling frequency (sampling theorem). We will investigate what happens if we deliberately violate this rule (aliasing effect).
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