ESTIMATION OF PEAK GROUND ACCELERATION OF RANAU BASED ON RECENT EARTQHUAKE DATABASES

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