Information Technology Reference
In-Depth Information
-curves whose low-frequency branches are weakly distorted
at most stations. If the dispersion relations exist between the apparent-resistivity
and phase curves, we hardly lose any substantial information while rejecting the
longitudinal
longitudinal phase
-curves reduces to an elimina-
tion of branches which violate the dispersion relations or are suspected of three-
dimensional distortions.
The TP model derived from the inversion of the Re W zy - and Im W zy -curves
is used as a starting model for the longitudinal phase inversion. The inver-
sion
-curves. The normalization of the
-curves
of
the
results
in
the
TE
model
shown
in
Fig.
12.64.
The
model
misfits
are
presented
in
Table
12.3,
where
is
the
phase
misfit
(rms deviation of the model values from the observed values), while
=
max
characterizes the maximum variation of the observed phase
values. At most stations, the phase misfits are 5 to 10 times less than the
phase maximum variation, indicating good agreement between the model and
observations.
Compare the continental segments of the TE and TP models. The TE model
differs from TP model by better resolving the crustal conductive layer (25-
45 km, 14-46 Ohm
min
·
m) and the subvertical mantle conductive zone (45-110
km,
= 12-46 Ohm
·
m).
We
can
consider
the
TE
model
as
an
edited
TP
model.
Level III. Inversion of
(TM-mode). The transverse apparent resistivi-
ties and phases are less sensitive to crustal and mantle conductive zones but they may
provide sharp estimate of the resistivity of the upper consolidated crust and reveal
the electric connection between the downgoing oceanic plate and crustal conductive
layer.
The inversion of the TM-mode is performed using the TE-2 model derived from
the inversion of the TE-mode as a starting model. It results in the TM model shown
in Fig. 12.65. The model misfits are presented in Table 12.4, where
and
are
misfits of transverse apparent resistivities and phases (rms deviation of the model
values from the observed values), while while
and
charac-
terizes the maximum variation of the observed phase values. The apparent resistivity
misfits at most stations vary from 6 to 12%, and the phase misfits are 7-10 times
smaller than the maximum phase variation.
The TM model inherits the main features of the starting TE model (although with
some deviations). What does the TM model indicate? First, there is no continuous
ellectrical connecton between the downgoing oceanic plate and the crustal conduc-
tive layer (a conductive coupling is absent). Second, the upper consolidated crust in
the continental segment of the model has a resistivity of about 2000 Ohm
= max
min
·
m (not
very high).
To complete the interpretation, we analyze the TP, TE, and TM models and con-
struct the generalized model EMSLAB-III, smoothing out insignificant details and
enlarging blocks. All changes are controlled by local misfits. The resulting gener-
alized model EMSLAB-III is shown in Fig. 12.66. Look at Fig. 12.67, where the
model and observed curves of
, , , ,
Re W zy , and Im W zy are compared
is eliminated by a vertical displacement
(the static shift in the observed curves of
Search WWH ::




Custom Search