Editing Spectral induced polarisation (section)

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'''Spectral induced polarization''' ('''SIP'''), or '''complex resistivity''' ('''CR''') and also '''complex conductivity''' ('''CC'''), is a [[geophysical survey]] technique and an extension of the [[induced polarization]] (IP) method, being itself an extension of measuring the Earth's resistance at a single frequency or under [[direct current]] (DC) (a technique commonly known by the name [[Resistivity logging|resistivity]]).<ref name="Reynolds_1997"/> SIP measures the frequency-dependent (i.e. [[spectrum|spectral]]) complex [[electrical impedance|impedance]], equivalent to the amount of [[electrical resistance|resistance]] and [[phase (waves)|phase shift]] between electric [[current (electricity)|current]] and [[voltage]]. The usual frequency range for [[alternating current]] (AC) applied during SIP surveys is tens of [[kHz]] to [[MHz]]. As with other geophysical methods, SIP aims to distinguish material properties of the subsurface, such as [[salinity]] and [[aquifer|saturation]].