Warta Geologi, Vol. 46, No. 2, August 2020, pp. 59–68
Earth crustal analysis of Northwest Sabah region inferred
from receiver function method
Abdul Halim Abdul Latiff*, Faridah Othman
Geosciences Department, Universiti Teknologi PETRONAS, 32610
Bandar Seri Iskandar, Perak, Malaysia
*Corresponding author email address:
abdulhalim.alatiff@utp.edu.my
Abstract:
Many methods are used to investigate the Earth’s crustal with the knowledge of
geology and geophysics. Earth crustal analysis beneath the Kota Kinabalu
region, located in Northwest Sabah, was performed by using tele-seismic
earthquakes as sources. While Sabah geology is highly complex the understanding
of its tectonic history has remained ambiguous. The tomography of the Kota
Kinabalu region is mainly influenced by the collision between the South China
Sea and Sabah margins during the Early Miocene which leads to crustal
thickening. At present, the subsurface properties, and structures underlying
the Kota Kinabalu region are yet to be recognized. Thus, this study aims to
acquire the crustal properties beneath the Kota Kinabalu region through the
deployment of a weak-motion seismometer station within the Crocker Range,
Sabah, Malaysia. Additionally, the work conducted is to determine the thickness
and velocity layer of the Earth’s crust up to the Moho boundary. Receiver
function analysis was chosen as the method to conduct this study where responses
of tele-seismic earthquakes recorded at KKM station were evaluated and
processed through 2D rotation, iterative time deconvolution, signal-to-noise
ratio analysis, stacking, H-k analysis, as well as forward modelling and
waveform inversion. A total of 916 time series data were retrieved from
International Seismological Centre (ISC)’s respiratory with only 184 receiver
functions were incorporated in this study whereas the remaining 732 receiver
functions were deemed noisy and unfit for the next process. The selected
receiver functions have an earthquake magnitude greater than 6 mb with a
signal-to-noise ratio of greater than 5. The processing steps included in this
study are conducted by using open-source computation programs such as Seismic
Analysis Coding (SAC) and Generic Seismic Application Coding (GSAC). From the
1-D velocity models inferred from receiver function inversion, the subsurface
structural framework and velocity anomalies within the crust beneath the
station were interpreted and analysed. With the additional information
generated from H-k analysis, it is interpreted that the Earth subsurface
beneath the Kota Kinabalu region has the Conrad discontinuity at 26 km depth,
the Moho boundary at 40 km depth while the Lithosphere-Asthenosphere boundary
was found at 66 km below the surface level. Additionally, the velocity profiles
within the Kota Kinabalu’s crust show alternating patterns with VP
has the range between 5 km/s to 7 km/s, and VS has the range of 3
km/s to 4 km/s. The VP and VS readings reached 8 km/s and
4.5 km/s respectively as it hits the Moho boundary at 40 km depth.
Keywords:
Receiver function, crustal thickness, velocity structure, Kota Kinabalu
DOI :
https://doi.org/10.7186/wg462202004
ISSN
0126–5539; e-ISSN 2682-7549
