# The 2010 National Seismic Hazard Model

The latest version of the National Seismic Hazard Model (NSHM) for New Zealand provides probabilistic estimates of the strength of earthquake shaking that can be expected according to a user-defined time period and probability, e.g. the peak ground acceleration (PGA) that has a 10% chance of happening in any 50 year time window. Probabilistic Seismic Hazard Analysis (PSHA) uses the location, recurrence behaviour, and predicted ground motions of earthquake sources to estimate the hazard at a site, or across a grid of sites as shown in the map below for Class C (shallow soil) site conditions.

The NSHM is an algorithm that draws upon several component models to calculate its results. It uses a fault model that combines New Zealand’s active fault database, which includes 536 fault sources, and the 170 year historical earthquake catalogue. The background model is comprised of a multi-layered background seismicity grid.

Ground Motion Prediction Equations (GMPEs) are also an important component of the NSHM. The standard GMPE in use in New Zealand outside of the Christchurch region is the McVerry et al. (2006) GMPE.

**The source model files can be downloaded here F501111U.DAT and here NZBCK615.DAT. **

The previous version of the fault source model file is F501115B.DAT. The background model source file has not changed at this time.

**A version of these models formatted for OpenQuake can be downloaded here:**

This model has been included in the Global Earthquake Model (GEM) Foundation’s global model mosaic. Further information can be found here: https://hazard.openquake.org/gem/models/NZL/

Additional information and updates regarding the models will follow soon.

**See below for a list of relevant source model citations.**

**Fault Source Model (file = F*.DAT)**

Rows 1-3: Ignore

Row 4: Abbreviated fault source name and slip type

rv, rs = reverse

sr = strike-slip and reverse

ss = strike-slip

sn = strike slip and normal

nn, ns = normal

nv = normal-volcanic

if = subduction interface

Row 5: Number of digital straight-line sections (n) making up the source

Row 6: Dip, dip direction, depth to base, depth to top

Row 7: Endpoints of fault source in degrees and mins, characteristic Mw, and mean/preferred recurrence interval

Rows 8 to (8+n-1): Endpoints of digital straight line sections making up fault source (one row per digital section)

Row 8+n-1: End of fault source delimiter

**Background Source Model (File = NZBCK*.txt)**

Row 1:

Columns 1-6: Three “subcatalogues”, giving min magnitudes and time periods of completeness; i.e.

4.0 46 = M>4.0 for the time period 1964-2009 inclusive

5.0 24 = M>5.0 for the time period 1940-1963 inclusive

6.5 100 = M>6.5 for the time period 1840-1939 inclusive

Column 7: Magnitude increment (0.1)

Rows 2 to end of file:

Columns 1-3: “Nvalues” for the three subcatalogues above, i.e.

N(M>4 for 46 years) N(M>5 for 24 years) N(M>6.5 for 100 years)

Column 4: b-value

Column 5: Maximum magnitude for point source

Column 6*: Percentage crustal events

Column 7: Slip type (same as fault model, listed above)

Column 8*: Percentage slab events

Column 9*: Percentage interface events

Column 10-12: Latitude, longitude, and depth of point source. Note that the point sources are spaced evenly in lat, lon, and depth, and the N values are defined for a volume that has boundaries equidistant between the point source and the immediate neighbours.

* The values in these columns should sum to 1 (100%).

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**Relevant Citations **

Stirling, M.W.; McVerry, G.H.; Gerstenberger, M.C.; Litchfield, N.J.; Van Dissen, R.J.; Berryman, K.R.; Barnes, P.; Wallace, L.M.; Villamor, P.; Langridge, R.M.; Lamarche, G.; Nodder, S.; Reyners, M.E.; Bradley, B.; Rhoades, D.A.; Smith, W.D.; Nicol, A.; Pettinga, J.; Clark, K.J.; Jacobs, K. 2012 National seismic hazard model for New Zealand : 2010 update. *Bulletin of the Seismological Society of America, 102(4): *1514-1542; doi: 10.1785/0120110170

Stirling, M.W.; McVerry, G.H.; Berryman, K.R. 2002. A new seismic hazard model for New Zealand, *Bulletin of the Seismological Society of America, 92(5)*:1878-1903.

McVerry, G.H.; Zhao, J.X.; Abrahamson, N.A.; Somerville, P.G. 2006. New Zealand Acceleration Response Spectrum Attenuation Relations for Crustal and Subduction Zone Earthquakes, *Bulletin of the New Zealand Society for Earthquake Engineerng, 39(1)*: 1-58.

**NOTE**:A correction was made to the site term equation (equation 4) of this paper. A PDF of the corrected equation can be found here:
SITE_TERM_CORRECTION.pdf (20.34 kB)