Translations:Sampling geophysical data/9/en

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As we mentioned above, this phenomenon is called aliasing. Recall that for a given sampling rate, there exists the so-called Nyquist frequency. The Nyquist frequency is defined as one-half the sampling rate. In our case, the sampling interval is 0.004 s, so the sampling rate is 1/0.004 = 250 samples/s. Hence, the Nyquist frequency is 250/2 = 125 Hz. Any signal above the Nyquist frequency takes on a disguise, or alias, because of the sampling. For example, a sine wave of 250 Hz has the alias in the sampled signal.