2010 National Seismic Hazard Model - NSHM

Database

This model 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.

Overview

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.

This model has been included in the Global Earthquake Model (GEM) Foundation’s global model mosaic(external link).

Seismic hazard pga graphic
This map from Stirling et al. (2012) shows PGA (units of g) with a 10% probability of exceedance in 50 years for NZS Class C (shallow soil) sites, produced using the 2010 National Seismic Hazard Model.

  • How to read the files

    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%).

  • Downloads

    Download source model files:

     

    Download a version of these models formatted for OpenQuake (ZIP, 532 KB)

Cite as: 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

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