Site object

Module openquake.hazardlib.site defines Site.

class openquake.hazardlib.site.FilteredSiteCollection(indices, complete)

A class meant to store proper subsets of a complete collection of sites in a memory-efficient way.

Parameters:

• indices – an array of indices referring to the complete site collection
• complete – the complete site collection the filtered collection was derived from

Notice that if you filter a FilteredSiteCollection fsc, you will get a different FilteredSiteCollection referring to the complete SiteCollection fsc.complete, not to the filtered collection fsc.

backarc

Extract backarc array from FilteredSiteCollection

expand(data, placeholder)

Expand a short array data over a filtered site collection of the same length and return a long array of size total_sites filled with the placeholder.

The typical workflow is the following: there is a whole site collection, the one that has an information about all the sites. Then it gets filtered for performing some calculation on a limited set of sites (like for instance filtering sites by their proximity to a rupture). That filtering process can be repeated arbitrary number of times, i.e. a collection that is already filtered can be filtered for further limiting the set of sites to compute on. Then the (supposedly expensive) computation is done on a limited set of sites which still appears as just a SiteCollection instance, so that computation code doesn’t need to worry about filtering, it just needs to handle site collection objects. The calculation result comes in a form of 1d or 2d numpy array (that is, either one value per site or one 1d array per site) with length equal to number of sites in a filtered collection. That result needs to be expanded to an array of similar structure but the one that holds values for all the sites in the original (unfiltered) collection. This is what expand() is for. It creates a result array of total_sites length and puts values from data into appropriate places in it remembering indices of sites that were chosen for actual calculation and leaving placeholder value everywhere else.

Parameters:

• data – 1d or 2d numpy array with first dimension representing values computed for site from this collection.
• placeholder – A scalar value to be put in result array for those sites that were filtered out and no real calculation was performed for them.

Returns:

Array of length total_sites with values from data distributed in the appropriate places.

filter(mask)

Create a FilteredSiteCollection with only a subset of sites from this one.

Parameters:mask – Numpy array of boolean values of the same length as this filtered sites collection. True values should indicate that site with that index should be included into the filtered collection. Returns:A new FilteredSiteCollection instance, unless all the values in mask are True, in which case this site collection is returned, or if all the values in mask are False, in which case method returns None. New collection has data of only those sites that were marked for inclusion in mask.

See also expand().

lats

Extract lats array from FilteredSiteCollection

lons

Extract lons array from FilteredSiteCollection

mesh

Return a mesh with the given lons and lats

sids

Extract sids array from FilteredSiteCollection

total_sites

The total number of the original sites, without filtering

vs30

Extract vs30 array from FilteredSiteCollection

vs30measured

Extract vs30measured array from FilteredSiteCollection

z1pt0

Extract z1pt0 array from FilteredSiteCollection

z2pt5

Extract z2pt5 array from FilteredSiteCollection

class openquake.hazardlib.site.Site(location, vs30, vs30measured, z1pt0, z2pt5, backarc=False, id=0)

Site object represents a geographical location defined by its position as well as its soil characteristics.

Parameters:

• location – Instance of Point representing where the site is located.
• vs30 – Average shear wave velocity in the top 30 m, in m/s.
• vs30measured – Boolean value, True if vs30 was measured on that location and False if it was inferred.
• z1pt0 – Vertical distance from earth surface to the layer where seismic waves start to propagate with a speed above 1.0 km/sec, in meters.
• z2pt5 – Vertical distance from earth surface to the layer where seismic waves start to propagate with a speed above 2.5 km/sec, in km.
• backarc" – Boolean value, True if the site is in the subduction backarc and False if it is in the subduction forearc or is unknown
• id – Optional parameter with default 0. If given, it should be an integer identifying the site univocally.

Raises:

ValueError – If any of vs30, z1pt0 or z2pt5 is zero or negative.

Note

Sites are pickleable

class openquake.hazardlib.site.SiteCollection(sites)

A collection of sites.

Instances of this class are intended to represent a large collection of sites in a most efficient way in terms of memory usage.

Note

Because calculations assume that Sites are on the Earth’s surface, all depth information in a SiteCollection is discarded. The collection mesh will only contain lon and lat. So even if a SiteCollection is created from sites containing depth in their geometry, iterating over the collection will yield Sites with a reference depth of 0.0.

Parameters:sites – A list of instances of Site class.

backarc

backarc array

expand(data, placeholder)

For non-filtered site collections just checks that data has the right number of elements and returns it. It is here just for API compatibility with filtered site collections.

filter(mask)

Create a FilteredSiteCollection with only a subset of sites from this one.

Parameters:mask – Numpy array of boolean values of the same length as this sites collection. True values should indicate that site with that index should be included into the filtered collection. Returns:A new FilteredSiteCollection instance, unless all the values in mask are True, in which case this site collection is returned, or if all the values in mask are False, in which case method returns None. New collection has data of only those sites that were marked for inclusion in mask.

See also expand().

classmethod from_points(lons, lats, site_ids, sitemodel)

Build the site collection from

Parameters:

• lons – a sequence of longitudes
• lats – a sequence of latitudes
• site_ids – a sequence of distinct integers
• sitemodel – an object containing the attributes reference_vs30_value, reference_vs30_type, reference_depth_to_1pt0km_per_sec, reference_depth_to_2pt5km_per_sec, reference_backarc

indices

The full set of indices from 0 to total_sites - 1

mesh

Return a mesh with the given lons and lats

vs30

vs30 array

vs30measured

vs30measured array

z1pt0

z1pt0 array

z2pt5

z2pt5 array

openquake.hazardlib.site.eq(array1, array2)

Compare two numpy arrays for equality and return a boolean

openquake.hazardlib.site.prop

Extract sids array from FilteredSiteCollection