A preliminary study of seismic hazard condition for recent earthquake activities on Sumatra Island

Abstract

The active tectonic condition in Sumatra Island has generated several significant earthquakes followed by massive losses. Therefore, the seismic hazard scheme must be carefully conducted. Here, we analyzed the hypocenters distribution by relative relocation for stochastic analysis with machine learning to determine the seismic hazard condition. The well-relocated hypocenters figure several clusters ranging from 20 – 40 km to the megathrust zone to 0 – 20 km to the active faults. Total earthquakes were reduced from 12111 to 6598 after decluttering, which provided the values of magnitude completeness of 4.3, a value of ~8.4, and b-value of 0.98, indicating a highly stressful condition. The peak ground acceleration in Sumatra Island for 10% and 2% in 50 years range with the highest values of 0.6 – 0.8 gal along active faults while the lowest value with 0.0 – 0.3 gal in the megathrust zone. An example of observation from the crustal earthquake in Langsa city suggests an important validation between numerical model and observation. A similar condition between the model and observation will provide a good concept that can be used to construct a mitigation plan.