Sites

The sites at which to perform hazard and related calculations may be defined in a variety of ways. Examples of the file formats described below are available in the resource directory: etc/nshm.

Note on Coordinates: nshmp-haz supports longitude and latitude values in the closed ranges [-360° ‥ 360°] and [-90° ‥ 90°]. Note, however, that mixing site and/or source coordinates across the antimeridian (the -180° to 180° transition) will yield unexpected results. For Pacific models and calculations, always use positive or negative longitudes exclusively.

Site String

In the simple case where there is a single site of interest, most nshmp-haz programs accept a comma-delimited string of the form: name,lon,lat[,vs30,vsInf[,z1p0,z2p5]], where vs30, vsInf, z1p0, and z2p5 are optional. Note that if vs30 is supplied, so too must vsInf. Likewise if z1p0 is supplied, so too must z2p5. If the string contains any spaces, escape them or wrap the entire string in double quotes.

For any site parameter values that are not supplied on the command line or in the file formats below, the following defaults are used (see the site defaults configuration):

    name: Unnamed
    vs30: 760.0
   vsInf: true
    z1p0: NaN (GMM will use default basin depth model)
    z2p5: NaN (GMM will use default basin depth model)

Comma-Delimited Format (*.csv)

• Header row must identify columns.
• Valid and [optional] column names are:
  [name,] lon, lat [, vs30] [, vsInf] [, z1p0] [, z2p5]
• At a minimum, lon and lat must be defined.
• Columns can be in any order and any missing fields will be populated with the default values listed above.
• If a site name is supplied, it is included in the first column of any output curve files.

GeoJSON Format (*.geojson)

Although more verbose than the comma-delimited format, GeoJSON is a more versatile format for encoding geographic data. Moreover, GeoJSON files are rendered directly on GitHub providing immediate visual feedback as to the contents of a file. See the GitHub GeoJSON page for more information.

nshmp-haz uses GeoJSON for both lists of sites and to define map regions. If you encounter problems when formatting JSON files, use JSONLint or GeoJSONLint for validation.

Site Lists

A site list is expected as a Point FeatureCollection. For example:

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "Point",
        "coordinates": [-122.25, 37.80]
      },
      "properties": {
        "title": "Oakland CA",
        "vs30": 760.0,
        "vsInf": true,
        "z1p0": 0.048,
        "z2p5": 0.607
      }
    }
  ]
}

As with the CSV format, the minimum required data is a geometry coordinates array. All properties are optional. When using GeoJSON, the title property maps to the name of the site. Additional properties, if present, are ignored by nshmp-haz but permitted as they may be relevant for other applications. For example, styling properties may be used to improve rendering on GitHub and elsewhere.

For a fully fledged example, see the NSHM test sites file.

Map Regions

GeoJSON is also used to define nshmp-haz map regions. For example, see the file that defines a region commonly used when creating hazard and other maps for the Los Angeles basin.

A map region is expected as a Polygon FeatureCollection. Currently, nshmp-haz only supports a FeatureCollection with 1 or 2 polygons. When a single polygon is defined, it must consist of a single, simple closed loop. Additional arrays that define holes in the polygon (per the GeoJSON spec) are not processed and results are undefined for self-intersecting coordinate arrays. This polygon feature supports the same (optional and/or extra) properties as the Point features described above. The site properties are applied to all sites in the defined region. In addition, this feature must define a spacing property with a value in decimal degrees that governs the site density within the region. This polygon defines the area over which hazard calculations are to be performed.

A second polygon may be used to define a map region. This polygon must be defined first, must have a feature id of Extents, and must be rectangular (in a mercator projection) with edges parallel to lines of latitude and longitude. This polygon is used primarily when outputting hazard curves in the USGS binary format. Any points in the 'calculation' polygon outside the 'extents' polygon are ignored; hazard values at any points within the 'extents' polygon but outside the 'calculation' polygon are set to zero. For an example, see the NSHMP Western US map site file.

Next: Source Models