Schmucker-Weidelt Lecture Notes, Aarhus, 1975 - MTNet

'periments are done with profiles or arrays, the data y = y(R,t)
permit a structural sounding of the property m = F(z) + Am(r)
with particular emphasis on lateral variations Am(2).
- .
Here m(z) represents either a global or regional mean distribution.
It may also be the result of vertical soundings at "normal sLtesn
wheqzthe surface data show no indications for lateral variations
of m. Since the dependence of y(R,t) - on m(r) - will be non-linear,
anomalies Ay(R,t)
and
-
-. = y(R,t) - yn(t) will be dependent on Am -
m(z) , i.e. the inierpretation of. second-type -data must proceed on
the basis of a known mean or nornlal distribution F(z) consistent
with data yn("c at a normal site. It should be noted that in the
case of static data of the first type usually no ii~terdependence
between Ay and will exist, i.e, the interpretation of their
anomalies is gependent of global or regional mean distributions
of the relevant property n.
Suppose that for data of the second type the lateral variations
bm(r) - are small in relation to G(z). Then the results of vertical
soundings at many different single sites may be combined to -
approximate a structural distribution m = m + Am. For geomagnetic
induction data the relevant property, namely the electrical. re-
sistivity has usually substantial lateral variations and a one-
dimensional intezpretation as in the case of vertical soundings
will not be adequate. Instead a truly multi-dimensional inter-
pretation of the data is required which is to be based on "normal
data" at selected sites (cf. 8.2). Such normal sites are her@ rather
the exception than the rule.
7.2 The data and physicai properties of internal matter which
are involved
The Earth's magnetic field is subject to small fluctuations g(rtt).
.
They arise from primary sources in the high atmosphere and from
seconda-y sources within the Earth. At the Earth's surface their '
r. amplitude is
-