## Publication 14

##
On the equivalence of the ``Niblett'' and ``Bostick'' transformations in the
magnetotelluric method

###
Alan G. Jones

### Abstract

In the 1D interpretation of magnetotelluric data, it is
often useful to discover a reasonable first-approximation
to the true conductivity-depth distribution beneath
the recording location. This may be undertaken in the
field, in order to ascertain if the station spacing is satisfactory
or whether a greater station density of coverage
is required, or at the base laboratory, as a prelude to a
more sophistocated 1D inversion of the data.
There are three approximations presently in use by
workers whose interest lies in the conductivity structure of
the earth: (1) the Schmucker rho*-z* scheme (Schmucker,
1970); (2) the Bostick transformation (Bostick,
1977); and (3) the Niblett approximation (Niblett and
Sayn-Wittgenstein, 1960). The first two are in widespread
use in western Europe and north America, whilst
the Niblett approximation appears to be strongly favoured
in eastern Europe and the USSR.
Weidelt et al. (1980) have previously detailed the relationship
between Schmucker's rho*-z* and. Bostick's
transformation; it is the purpose of this letter to demonstrate
that Bostick's transformation and Niblett's approximation
are very equivalent - they give exactly the
same resistivity-depth profiles!

### Source

*Journal of Geophysics (Zeitschrift fuer Geophysik)*, **53**, 72-73.

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Alan G Jones / 28 February 2010 /
alan-at-cp.dias.ie