Probabilistic seismic hazard map of Papua New Guinea

Abstract

We developed a probabilistic seismic hazard map of Papua New Guinea expressed in terms of peak ground acceleration with return period of 475 years. The calculations were performed for bedrock site conditions (Vs30 = 760 m/s). A logic-tree framework was applied to include epistemic uncertainty in the seismic source as well as ground motion modelling processes. Two seismic source models were developed using area source zones and smoothed seismicity, respectively. Based on available geological and seismological data, defined seismic sources were classified into four different tectonic environments. For each of the tectonic regimes three ground motion prediction equations were selected and used to estimate the ground motions at a grid of sites with spacing of 0.1° in latitude and longitude. Results show a high level of hazard in the coastal areas of Huon Peninsula and New Britain–Bougainville regions and a relatively low level of hazard in the southwestern part of Papua New Guinea. Seismic hazard disaggregation results show that in the Huon Peninsula region high seismic hazard is caused by modelled frequent moderate to large earthquakes occurring on the Ramu-Markham Fault Zone. In the New Britain–Bougainville region the distance to the subduction zone associated with the New Britain Trench mainly controls the calculated level of hazard. It is also shown that the estimated level of peak ground acceleration is very sensitive to the selection of ground motion prediction equations. Overall our results differ significantly from those of previous studies, and we surmise that these differences are due to our use of modern ground motion prediction equations and earthquake source information.