Abstract
The occurrence of earthquake with magnitude MW 6.0 in Ranau recently has triggered many questions regarding their nature of recurrence, characteristics in size and mechanism in and its surrounding region. In recent years, Sabah has witnessed an increase in low to moderate seismic activities due to the causative ground structures which reflected in their seismic productivities. Over the past years between 1900 until recently, magnitudes ranging from MW 2.9 to 6.0 were known to have occurred. While large magnitude earthquakes are fortunately rare, in the history of earthquakes, the region already experienced devastating earthquake including a magnitude of MW 5.8 on 26th July 1976 centred in Lahad Datu. The observation on earthquake catalogue spanning from 1900 to 2014 has been obtained from various earthquake data centers, Ranau previously recorded an earthquake with magnitude MW 5.1, the repeat over intervals of sudden large earthquake is considered to have much shorter recurrence intervals. This paper discusses the procedure for evaluating the probabilistic seismic hazard analysis (PSHA) whereas the peak ground acceleration (PGA) on bedrock of Ranau area for 10% and 2% probability of exceedance is taken into account. By analysing the correlation between the tectonic features and the available data on past seismicity, the estimation of PGA is based on smoothed-gridded seismicity with a subjectively chosen correlation distance of 50 km. The PGA estimation values for Ranau are approximately in the range of 80 to 140 cm/s2 that will be exceeded 10% probability of exceedance and 140 to 250 cm/s2 for 2% probability of exceedance.
Highlights
Sabah is considered as a stable continental shield region at the triple junction zone of convergence between the Philippine, Indian-Australian and Eurasian Plates
In accordance with the map, Ranau region shows that the peak ground acceleration (PGA) estimation for the region which is available for 10% probability of exceedance is between 80 and 160 cm/s2
The hazard maps are depicted in terms of peak ground acceleration (PGA) at bedrock level of 10% and 2% probability of exceedance in 50-year return period corresponds to 475 and 2,475 years, respectively
Summary
Sabah is considered as a stable continental shield region at the triple junction zone of convergence between the Philippine, Indian-Australian and Eurasian Plates. The recent earthquake occurred in Ranau with moment magnitude (MW) of 6.0 at a depth of approximately 10 km and lasted 30 seconds caused serious damage to many infrastructure and can felt as far as 400 km from the epicentre. This was the strongest and worst earthquake ever affected Malaysia since 1976 with approximately 8 people died due to this event. The earliest seismic hazard study for East Malaysia seismicity was based on intensities by a researcher [2]. In accordance with the map, Ranau region shows that the peak ground acceleration (PGA) estimation for the region which is available for 10% probability of exceedance is between 80 and 160 cm/s2.
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