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Underground conductivity structure in Tasmania

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Hermanto, MR (1985) Underground conductivity structure in Tasmania. Unspecified thesis, University of Tasmania.

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Abstract

Geomagnetic variations were measured at 35 temporary stations in the
north, north-east and centre of Tasmania. The surveys were carried out
from early in 1983 to the middle of 1984. The surveys were designed to
map the southern extension of the anomaly discovered by Buyung (1980) and
revealed two types of anomalies, i.e. inland and coast effect. The inland
anomaly is characterized by oppositely directed in-phase induction arrows
at close locations for periods from 4 to 20 minutes, indicating the
presence of a concentration of current in a highly conductive zone. This
anomaly is coincident with the Tamar Fracture Zone. Meanwhile, the
gradual change in the direction of induction arrows with increasing period
from various directions to almost south-east illustrates the significant
effect of the coast. This is probably due either to current induced in
the conducting ocean water or to high conductivity contrasts between the
resistive block in the eastern part of Tasmania and the conducting ocean
floor.
The finite difference method of Jones and Pascoe (1971) and Pascoe
and Jones (1972) was used to calculate the induction response of twodimensional
models and to interpret the observations. Modelling reveals
that a highly conductive zone, responsible for the inland anomaly, is
located at a depth, of about 2 km from the surface. This zone, which is
bounded by resistive blocks to the east and west, has a resistivity of 0.5.SL
m and thickness of 2 to 3 km. This model agrees with magneto-telluric
observations of previous workers. The most likely cause of this highly
conductive zone is a large quantity of saline water or conducting liquid in
porous or cracked rocks.
Analogue modelling of the coast effect around Tasmania by Dosso et
al. (in press) has been used in an attempt to isolate the effect of inland
structures. This was only partly successful, probably because the
analogue models assume that the island is a perfect insulator.

Item Type: Thesis (Unspecified)
Keywords: Earth resistance, Magnetic declination, Geology
Copyright Holders: The Author
Copyright Information:

Copyright 1985 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (M.Sc.)--University of Tasmania, 1985. Bibliography: leaves 107-111

Date Deposited: 19 Dec 2014 02:29
Last Modified: 11 Mar 2016 05:56
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