Translations:Sampling geophysical data/8/en

We can look at this problem from yet another viewpoint. Consider a 125-Hz sine wave sampled 125 times per second. There will be one sample per cycle. Depending on the time instant at which the first sample occurs, the first sample can have any value between –1 and +1 (i.e., the minimum and maximum values of the sine wave). Because the sampling rate is the same as the frequency of the sine wave, the sampling is precisely in step with the sine wave, and all other samples will have the same value as the first sample. Thus, the sampled data are flat and represent a zero-frequency signal. The sampling process with this rate of sampling has caused a 125-Hz signal to appear to be a 0-Hz signal.