The Neo-Deterministic Seismic Hazard map (NDSHA) of Sumatra compared with official 2010 and 2017 derived from PSHA method

Abstract

Typical seismic hazard problem lies on determination of ground motion characteristics associated with future earthquakes. Strong ground motion characteristics such as Peak Ground Acceleration (PGA) is important information for engineers in order to provide earthquake resistant building. The Indonesian government has provided update of maps of PGA by released a series official PSHA (Probabilistic Seismic Hazard Assessment) maps in 1978, 2002, 2010 and 2017. On the other hand, the NDSHA (Neo-Deterministic Seismic Hazard Assessment) method has been developed and successfully applied to Sumatra. Because of the availability of numerical PGA data for the official PSHA 2010 and 2017, this paper discusses the comparison of PGA between derived from NDSHA and that of official PSHA updated in 2010 and 2017. The spatial resolution of the PGA digital map of PSHA is 0.01 degree and NDSHA is 0.1 degree. Due to the different resolution, a program and a script are developed to incorporate PSHA data into the NDSHA data points by performing interpolation procedure. The comparison results show the PGA of PSHA 2017 is significantly greater than PGA PSHA 2010. However, the PGA values of the 2017 PSHA map are lower than that of PSHA 2010 such as along the Sumatran fault in Central and South Sumatra. The PGA values estimated by using standard NDSHA with 10 Hz cut-off is higher than those of the computed PGA from PSHA at PE (Probability of Exceeding) of 2% in 50 year for official map released in 2010 and 2017. For comparison with PE of 2% in 50 year, the near field NDSHA gives the PGA value greater than that of the PSHA; and for the far field sources. This means the NDSHA calculation for Sumatra gives reasonable results based on the adopted magnitude distance threshold. This is due to the fact that the standard NDSHA is based on the realistic physical simulation of the seismic wave propagation. The comparison between the PGA computed based on the proposed enhanced version of NDSHA and PSHA shows that the updated version gives the same values at near field and lower values at the far sites; whereas the standard one gives a higher value in NDSHA, which in turn gives a higher PGA value for the near and far field sources.