Velocity Dispersion Analysis of Shallow Crustal Structures North of Bukit Bunuh, Lenggong, Perak

In the Earth there is no such perfectly elastic medium. In an elastic medium, wave
particles that travel through the medium could be distorted due to velocity dispersion
and attenuation. Velocity dispersion is highly depends on several factors. The factors
could be: porosity, fractures, fluid mobility and also the scale of heterogeneities. In
2012, number of core samples was taken from Bukit Bunuh, Lenggong, Perak to
measure the velocity P-waves and S-waves of the cores in the laboratory. One
seismic reflection line was acquired in the outcrop back in May 2014. From the
previous final year project shows ‘hockey-stick’ effect once applied the specific
velocity ranges obtained in the laboratory for granite in velocity analysis for deep
area.
A series of experiments will be conducted to determine the velocity variation
of granite formation at West of Bukit Bunuh over as wide a frequency range as
possible. This project will cover two aspects; the geological structure of Bukit Bunuh
as well as the geophysical aspect whereby seismic data processing is the main focus
in this project. The experiments that will be conducted fall into two categories: (1)
Reflection survey measurement (10-250Hz) with dominant frequency of. 35Hz and
(2) Laboratory measurement (300-900kHz) with dominant frequency of 700kHz.
Difference ranges of frequencies applied in both field and laboratory measurement
are the main reason for velocity dispersion.
Further analysis of the velocity dispersion will show that the laboratory
velocity measurement cannot be directly applied to the reflection seismic data during
the velocity picking since both experiment were acquired by using different
frequency range. The application of the velocity obtained in laboratory to the
reflection data will show the hockey-stick effect instead of flattening the layers in
gathers.