2-D Electrical Resistivity, Seismic Refraction Tomography And Geotechnical Data Application In Searching For Ancient Impact Crater Of Bukit Bunuh, Perak
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Date
2015-05
Authors
Ismail, Nur Azwin
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Abstract
2-D electrical resistivity and seismic refraction are the geophysical methods
that measure the conductance of electrical current through Earth’s material and
propagation of shock wave in Earth’s subsurface respectively. The methods were
implemented at Bukit Bunuh, Perak to identify the boundary, type and size of ancient
impact crater with support of boreholes data and laboratory sample test. The research
studied about the relation between modification of the lithological and physical
properties of soils and rocks. The study divided into three stages which are regional
study, Western of Perak River and Eastern boundary of study area. Results show that
overburden layer is made up of alluvium which predominantly consists of silt, sand
and clay with existence of little gravel and fine soils. Suevite breccia also scattered
inside the crater. The crater is classified as a complex crater type with diameter of
4.5-5 km and few central uplifts/rebound zones detected almost at the center of the
crater. Crater rim/slumped terrace, inside and outside the crater are well defined by
outlining bedrock topography for the whole area. Standard parameter tables
correlating 2-D electrical resistivity, seismic refraction and geotechnical methods are
produced for inside crater, on the rim/slumped terrace and outside crater for impacted
soils and rock in the tropical region. Overburden layer outside the crater has uniform
and lower resistivity and velocity values compared to inside crater and on the
rim/slumped terrace. Slightly high resistivity and velocity of weathered granite
bedrock is observed inside crater while low resistivity is observed on the crater
rim/slumped terrace. High moisture content and low N value is identified inside
crater while low moisture content and high N value is acquired on crater rim/slumped
terrace and outside the crater. Empirical correlations are generated between
geophysical and geotechnical parameters with reliable regression coefficient and
enhancement of empirical correlation of p-wave seismic velocity are also produced.
Through qualitative and quantitative analysis, a quick and cost effective way for
assessment of geological and geotechnical characteristics is introduced for better
understanding and discovery of Bukit Bunuh ancient impact crater. A 2-D geological
cross section is produced by transforming 2-D electrical resistivity results with
support of p-wave seismic velocity section and geotechnical parameters for West-
East line. Correlations between geophysical and geotechnical parameters provide a
new insight into various geological sequence and structure of subsurface soils and
rocks of tropical region of Bukit Bunuh.
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Keywords
Geotechnical Data Application , Bukit Bunuh, Perak