Identification Of Seulimeum Fault Aceh Indonesia And Bok Bak Fault Kedah Malaysia By Electrical And Magnetic Mapping
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Date
2015-06
Authors
KAMARUDDIN, NUR AMINUDA
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Abstract
A natural disaster is part of the dynamic interactions of the Earth’s structures.
For example, the earthquake occurred for the reason that interactions between
moving plates which probably being pushed or pulled. The present tectonic structure
of Sumatra mainly results from the subduction at the Sunda trench. Sunda trench is
the subduction zone where the continental Sunda plate was subducted under oceanic
Indian-Australia plate. The objective of this study is to study the signatures of
Seulimeum fault which segmented from the Sumatran fault (Indonesia) and Bok Bak
fault which located at the northern part of Peninsular Malaysia. Two geophysical
methods chosen are electrical and ground magnetic methods. There were four and
five electrical survey lines were done crossing Seulimeum and Bok Bak fault
respectively. Magnetic rover stations were done randomly with spacing roughly
about 100 m surrounded both selected faults. Therefore, the signatures focused in
term of resistivity, chargeability and magnetic. The fault was identified from the
resistivity result by the contrast resistivity value and the fault zone with thick
overburden. The overburden within fault zone consists of geological materials such
as breccias and gouge. The resistivity value within the Seulimeum fault zone is 0.1-
10 Ωm. Besides, the low chargeability value (0.01-5 msec) was identified only at the
upper part within the fault zone and the rest is high chargeability value (>100 msec)
which probably due to great influences of bedrock geology. From the magnetic
residual contour map, the long dislocations from southeast to northwest direction
with contrast of high and low magnetic residual value of -150 nT to 150 nT. In
addition, the graph profile of magnetic residual was plotted with bedrock and ground
topography to see the pattern of magnetic and the overburden thickness within fault
zone. The profiles show that the magnetic response is decreasing within the
suspected fault zone. With the same goals, the Seulimeum fault becomes a model to
the Bok Bak fault by employing the same geophysical methods. The resistivity value
within the Bok Bak fault zone is 5-100 Ωm. Besides, the high chargeability value of
>80 msec identified within the fault zone with some low chargeability value of 0.01-
5 msec was identified at the upper part. From the magnetic residual contour map, the
contrast of high and low magnetic residual value of -5 nT to 15 nT perhaps indicates
the fault zone. Lastly, the profiles show that the response is decreasing within the
suspected fault zone as well. Hence, the results shown by the Bok Bak fault exhibit
the same signatures presented by the Seulimeum fault which the fault zone indicated
by low resistivity value, high chargeability and low magnetic response. The
geological sediments within fault zones perhaps came from the geological sediments
outside the fault zone as they comprises the same value of resistivity, chargeability
and magnetic.
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Keywords
Identification Of Seulimeum Fault Aceh Indonesia And Bok Bak Fault Kedah Malaysia , By Electrical And Magnetic Mapping