Seismic Hazard Function (SHF) study of coastal sources of Sumatra Island: SHF evaluation of Padang and Bengkulu cities

Abstract

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.

Earthquake Potential Hazard Analysis of Palembang City, Sumatra Island

“…In this study, the data used are based on the results of Triyoso et al (2020) for earthquake sources around megathrust, where the A-value model of Gutenberg-Richter (1944) was estimated based on the product of normalized seismic moment rate with mean seismicity smoothing. The correlation distance is 25 km, 50 km, and 150 km of shallow earthquake data of Mw ≥ 5.0, H ≤ 50-km of 1963 to 2016.…”

“…Following the previous study, seismic hazard assessment based on a seismicity smoothing using Gaussian function approach (e.g. Frankel, 1995;Petersen et al, 2008;Triyoso and Shimazaki, 2012;Triyoso et al 2020) was implemented. First of all, gridding was done on the area to be studied, then the number (n i ) of earthquake events with a magnitude greater than or equal to the reference (M ref ) was counted in each grid.…”

“…In constructing the probabilistic seismic hazard map expressed by peak ground motion defined as PGA or PGV, the GMPE is needed in terms of PGA or PGV as a function of magnitude and distance. The GMPEs are based on the result summarized in Triyoso et al (2020) in which the GMPEs of Zhao et al (1997) and Atkinson and Boore (2006) were used for subduction sources, (Natawidjaja and Triyoso, 2007). The GMPE of Fukushima and Tanaka of 1990 is updated with the GMPE of Fukushima and Tanaka of 1992, for strike-slip sources.…”

“…In this study, the SHF of Palembang City was analyzed on the basis of the influence of the subduction zone sources, strike-slip faults, and earthquake sources with intermediate to deep hypocentres. The seismicity rate model around the subduction sources and other shallow earthquake sources with the depth of less than and equal to 50 km was based on the integrated source model of Triyoso et al (2020). The strike-slip fault sources were modeled on the basis of seismicity smoothing algorithm (Frankel, 1995).…”

“…The PGA of 10% probability exceedance level for fifty-year period was analyzed for Palembang City, in which PGA value was obtained by applying several Ground Motion Prediction Equations (GMPE). They are based on Triyoso et al (2020) for subduction sources, Natawidjaja and Triyoso (2007) for strike-slip sources, and the GMPE of Atkinson and Boore (2003) for intermediate to deep earthquake sources. Furthermore, the amplification factor was estimated, and then incorporated into the PGA estimated.…”