Papua New Guinea (PNG)

Authors:

H. Ghasemi, C. McKee, M. Leonard, P. Cummins, M. Moihoi, S. Spiliopoulos, F. Taranu, E. Buri

For any additional information about this model please contact: chris_mckee@mineral.gov.pg

Summary

The model covering Papua New Guinea was developed within a collaboration between the Port Moresby Geophysical Observatory and Geoscience Australia; see Ghasemi et al. (2016). The original construction of the model is compatible with the OpenQuake (OQ) engine.

Information about the OQ model versions and input files can be found on the Results and Dissemination page.

Interactive Viewer

The viewer below depicts the seismic sources and hazard results in terms of PGA for a return period of 475 years. Click on the menu in the upper right corner to select the layer.

viewer_legend

Tectonic overview

Papua New Guinea sits at the convergent boundary between the Australian continent and the crust of Oceania. Throughout most of the island of New Guinea, the convergence is expressed as reverse faults which uplift the New Guinea Highlands. These faults extend west into the sea, and include the Ramu Markham Thrust, which may be the fastest-slipping continental fault known. In the east, the D'Entrecasteaux-Woodlark spreading ridge comes ashore near the Owen Stanley Range, producing rapid normal faulting as well. Offshore, both subduction and extension of the region's complicated oceanic plate boundary systems lead to additional seismic hazard.

Basic Datasets

Please refer to Ghasemi et al. (2016).

Hazard Model

Seismic Source Characterisation

The Global Hazard Mosaic implementation of the Ghasemi et al. (2016) model uses equal weighting between two logic tree branches:

  • Branch 1: All occcurrrences modelled as smoothed seismicity (point sources)
  • Branch 2: Seismicity occurring on two subduction interfaces (complex faults), with remaining seismicity modelled as area source zones (area sources)

Branch 1, smoothed seismicity

This branch includes point sources that model the distribution of seismicity over a 0.1° grid. The model includes two depth layers: shallow seismicity, smoothing earthquakes in the depth range of 0-50 km; and deep, which uses depths 51-100 km. A fixed b-value of 0.89 is used throughout, and the a-value computed based on the number of earthquakes in each grid cell as a fraction of the total seismicity, based on the method of Frankel (1975). Mmin is set to 5.0 everywhere, and Mmax is assigned from the encompassing area source zone polygon (discussed here as Branch 2). Nodal planes are assigned to match the closest resolved focal mechanism from the Global Centroid Moment Tensor catalogue.

Branch 2, subduction interfaces

Two subduction interfaces, listed in Table 1, are modelled as complex faults, which reflect the subduction geometry provided by Slab1.0 (Hayes et al., 2012). Ghasemi et al. (2016) note that these interfaces were originally modeled as area source zones (see next section); the occurrence rates and magnitude range reported in the published manuscript are still used. Both sources use Mw,min=5.0. Ruptures are assigned a purely reverse rake.

Subduction zone a-Value b-Value Mw,max
New Britian 6.0853 0.9320 8.8
Bougainville Island 5.9475 0.9370 8.8

Branch 2, area source zones

The remainder of seismicity is modelled in this branch as area sources, with occurrence parameters listed in Table 2 (which summarizes Table 2 in Ghasemi et al., 2016). All sources model Mw,min=5.0.

Area source zone a-Value b-Value Mw,max Tectonic region Depth (km) Strike(°)/dip(°)/rake(°)
0 5.0769 0.9390 8.2 Active shallow crust 27.5 300/45/90
1 5.9556 1.0340 8.0 Active shallow crust 25.0 120/45/90
2 5.7942 0.9900 8.5 Active shallow crust 15.0 100/45/90
3 5.4357 0.8550 8.2 Active shallow crust 20.0 100/90/0
4 5.6886 1.0770 8.2 Active shallow crust 27.5 80/45/90
5 4.1824 0.8120 7.8 Active shallow crust 27.5 90/90/0
6 5.3315 0.9330 8.2 Active shallow crust 27.5 30/45/90
7 4.9046 0.8790 8.4 Active shallow crust 22.5 90/90/0
8 4.9544 0.9560 8.0 Active shallow crust 25.0 60/90/0
9 5.8477 1.0410 8.0 Active shallow crust 27.5 90/45/90
10 5.4961 0.9170 8.2 Active shallow crust 20.0 270/45/90
13 5.1470 0.9130 8.7 Active shallow crust 15.0 315/45/90
14 5.1998 0.9550 8.4 Active shallow crust 17.5 90/45/90
15 5.5966 1.0080 7.6 Active shallow crust 10.0 90/90/0
16 4.6589 1.0410 7.6 Stable shallow crust 9.5 300/45/90
17 5.9798 1.0390 8.0 Active shallow crust 20.0 300/45/90
18 5.7021 0.9760 8.5 Subduction IntraSlab 100.0 315/45/90
19 6.2855 1.0430 8.5 Subduction IntraSlab 100.0 250/45/90
20 5.2880 1.0000 8.2 Subduction IntraSlab 100.0 270/45/90
21 5.7243 0.9520 8.2 Subduction IntraSlab 100.0 300/45/90
22 5.7318 1.1270 8.0 Subduction IntraSlab 100.0 300/45/90
23 5.5520 0.9990 8.5 Subduction IntraSlab 90.0 120/45/90

Ground Motion Characterisation

Active Shallow Crust Weight
Boore and Atkinson 2008 0.3
Chiou and Youngs 2008 0.3
Zhao et al. 2006 0.4
Stable Shallow Crust Weight
Toro et al. 2002[1] 0.5
Atkinson and Boore 2006 0.5
Subduction Interface Weight
Atkinson and Boore 2003 0.3
Youngs et. al. 1997 0.3
Zhao et. al. 2006 0.4
Subduction Intraslab Weight
Atkinson and Boore 2003 0.3
Youngs et. al. 1997 0.3
Zhao et. al. 2006 0.4

[1]: In the Global Hazard Mosaic implementation, we use a version of Toro et al. (2002) adapted to define a reference velocity of 800 m/s.

Results

Hazard curves were computed with the OQ engine on a grid of 10694 sites (spaced at approximately 10 km) with rock reference site condition, corresponding to a shear wave velocity in the upper 30 meters (Vs30) of 760-800 m/s. The computation was performed for peak ground acceleration (PGA), and spectral acceleration (SA) at 0.2s, 0.5s, 1.0s, and 2s.

The hazard map for PGA corresponding to a 10% probability of exceedance in 50 years (475 year return period), can be seen using the interactive viewer. For a more comprehensive set of hazard and risk results, please see the GEM Visualization Tools.

References

Frankel, A. (1995). Mapping seismic hazard in the central and eastern United States. Seismological Research Letters, 66(4), 8-21.

Ghasemi, Hadi, Chris McKee, Mark Leonard, Phil Cummins, Mathew Moihoi, Spiliopoulos Spiro, Felix Taranu, and Eric Buri. "Probabilistic seismic hazard map of Papua New Guinea." Natural Hazards 81, no. 2 (2016): 1003-1025.