Significant earthquakes on the island of Sumatra, Indonesia, have predominantly been earthquakes with a thrust mechanism that occurred due to the subduction process and seismotectonics near coastal cities of West and South Sumatra, which could be affected by earthquakes triggered by these seismic sources. We compared the Seismic Hazard Function (SHF) of two coastal cities of Sumatra: Bengkulu and Padang. The results showed that the SHF of Bengkulu is higher than that of Padang. Estimated earthquake hazards are presented in the form of seismic hazard maps expressed as the PGA of 10% rate of exceedance probability in 50 years. In estimating the seismic potential in Sumatra, the seismic moment rate was jointly estimated from the smoothed mean seismicity rate and the pre-seismic subduction surface strain rate model. In this study, the island of Sumatra was chosen as a master model for Seismic Hazard Analysis (SHA). The motivation for choosing Sumatra for the SHA was because of the large body of complete historical earthquake data of the North Western Sunda Arc. The SHF is calculated based on a magnitude range of 6.0 to 9.0 during 50 years with the radius distance from the source less than or equal to 100 km.
s s e l a a r , A lb e r t M . G . K l e in T a n k , G e r a r d V a n D er Sc h r ie r , M a r ia m a S. A b a s s , O m a r B a d d o u r , A r y a n F.V. V a n En g e l e n , A n d r e a Freire, P eer H e c h l e r , B a y u Im b a n g L a k s o n o , Iq b a l , R u d m e r Jil d e r d a , A n d r e K a m g a Fo a m o u h o u e , A rie K a t t e n b e r g , R o b e r t L e a n d e r , R o d n e y M a r t In e z G u i n g l a , A l b e r t S. M h a n d a , Ju a n Jose N ie t o , Su n a r y o , A ris Su w o n d o , Y u n u s S. Sw a r i n o t o , a n d G e V erver
Most of the destructive earthquakes in Sumatra are dominated by thrust mechanisms that occur due to the process of subduction and some earthquakes with strike-slip fault sources such as the Sumatra fault and northwestern Sumatra. Subduction zones along western Sumatra and Sumatran fault zones are active seismic sources of earthquake events. The seismotectonics of South Sumatra can be affected by earthquakes triggered by these seismic sources. In this study, an estimation and analysis of the potential for earthquake hazard curves were carried out in Palembang City due to the influence of subduction zone sources, strike-slip faults, and intermediate to deep earthquake sources. The algorithm of the seismicity smoothing was applied to estimate the seismicity rate for megathrust sources, active faults, and intermediate to deep earthquake sources. The smoothing algorithm is applied to estimate the seismicity rate for megathrust sources, active faults, and intermediate to deep earthquake sources. The earthquake hazard potential curve results showed that the estimated Peak Ground Acceleration (PGA) in the subduction earthquake sources bedrock was greater than the estimated ground shaking due to strike slip fault sources and intermediate to deep earthquake source. To understand better the potential ground shaking, the evaluation of PGA at the surface was then estimated by including the amplification factor. The amplification factor is calculated using the Horizontal-Vertical Spectral Ratio (HVSR) method. Based on the PGA estimated at the surface of 10% probability exceedance level during 50 years, the Palembang City has a potential shaking of around 35 gal, which is likely to be caused by a megathrust earthquake source.
The implementation of the Seismic Quiescence Index (SQI) into seismic hazard study and analysis mapped around the off southern coast of Sumatra - West Java. The 15 years of Region Time Length (RTL) were used in this study. To construct the SQI, first of all, we divided the period of the declustered shallow earthquake catalog of observation into two parts, i.e., a period of 1978 to 1992 and 1993 to June 2006. Two rate models were then developed to estimate the probability of a given magnitude and a specified time window. The result was then used to determine the probability difference between the two periods of observation and SQI estimation. The SQI then used better to understand the pattern of seismicity changes for PSHA. To construct the model for SHA is done by developing the seismicity rate model of the period 1978 to June 2006 and then weighted by the SQI index. Furthermore, the median Peak Ground Acceleration (PGA) of 10% probability exceedance level for 50 years is estimated and mapped. By incorporating an amplification factor, the PGA value on the surface can be determined. The amplification factor is calculated using the Horizontal-Vertical Spectral Ratio (HVSR) method. This result might be useful for better understand the future PSHA and mitigation before a large earthquake.
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