A probabilistic seismic hazard assessment for Sulawesi, Indonesia

Abstract

A probabilistic seismic hazard assessment that includes the effect of site amplification is undertaken for the island of Sulawesi, Indonesia. High seismic activity rates, both along fast-slipping crustal faults including the major Palu-Koro–Matano Fault System and in regions of distributed deformation, contribute to moderate–high earthquake hazard over all but the SW part of the island. Of particular concern in terms of seismic risk are the numerous cities sited on soft sedimentary basins that have formed due to movement along presently active structures and that can be expected to amplify earthquake ground motions, including the provincial capitals of Palu and Gorontalo.

Expert elicitation of model parameters for the 2018 National Seismic Hazard Assessment: Summary of workshop, methodology and outcomes.

“…fault sources are independent of area sources and their associated seismic moment rate simply added to that of the area sources); moment balanced (i.e. seismic moment rates were adjusted for area sources that envelope faults to preserve the total moment rate, as defined by instrumental seismicity within the area source (e.g., Cipta et al, 2017); and geometrically filtered (i.e. ruptures within the area source zone that intersected a 5 km buffer around the fault were considered non-physical, and removed from the area source model).…”

Distribution and morphology of the surface ruptures of the 2018 Donggala–Palu earthquake, Central Sulawesi, Indonesia

“…The PKF has been considered a significant source of the regional seismic hazard in Central Sulawesi due to a long fault trace over 200 km (Bellier et al 2006;Watkinson and Hall 2017), and frequent occurrences of large and moderate earthquakes (Mw 6-7.6) (Pelinovsky et al 1997;Go´mez et al 2000;Prasetya et al 2001). Based on this information, a probabilistic model for seismic hazard in Sulawesi has been proposed (Cipta et al 2017). However, records of this seismicity have been limited to minimal information on the year of occurrence, epicentre, and magnitude, and mostly contain vague information.…”

8. Earthquake sources of the Australian plate margin: revised models for the 2018 national tsunami and earthquake hazard assessments

“…The north arm is rotating rapidly clockwise relative to the stable Sunda Block and there are large variations in slip-rate and dip along strike (Silver et al, 1983a;1983b;Socquet et al, 2006;Cipta et al, 2016). Furthermore, the northern arm of Sulawesi can be divided into two rigid blocks separated by the strike-slip Gorontalo Fault (Socquet et al, 2006) As noted by Cipta et al (2016) contemporary seismicity is located down-dip 50-100 km south of the bathymetric expression of the trench. However, they caution against assuming the shallow dipping up-dip portion of the megathrust is aseismic.…”

“…Therefore we allow rupture all the way to the trench and vary slip-rate along the strike of the megathrust using the Euler poles of Socquet et al (2006). Dip at a depth of 20 km (18-24°) is estimated from Cipta et al's (2016) analysis of earthquake focal mechanisms while dips near the trench (2-16°) are taken from Silver et al's (1983b) analysis of seismic reflection profiles. Dip steepens to the east.…”

“…It is unclear if the Makassar Thrust should be modelled as one structure, or a series of thrusts. In this study we follow Cipta et al (2016) who model the fault as a single thrust fault accommodating 9 mm/yr of convergence between Sulawesi and Borneo on 30° dipping thrust faults. This source is considered unlikely to generate a tsunami with significant impacts on the Australian coastline, and so is not included in the PTHA18.…”