Source code for openquake.hazardlib.source.area

# The Hazard Library
# Copyright (C) 2012-2025 GEM Foundation
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
"""
Module :mod:`openquake.hazardlib.source.area` defines :class:`AreaSource`.
"""
import math
from openquake.hazardlib import geo, mfd
from openquake.hazardlib.source.point import PointSource
from openquake.hazardlib.source.base import ParametricSeismicSource


[docs]class AreaSource(ParametricSeismicSource):
    """
    Area source represents uniform seismicity occurring over a geographical
    region.

    :param polygon:
        An instance of :class:`openquake.hazardlib.geo.polygon.Polygon`
        that defines source's area.
    :param area_discretization:
        Float number, polygon area discretization spacing in kilometers.
        See :meth:`openquake.hazardlib.source.area.AreaSource.iter_ruptures`.

    Other parameters (except ``location``) are the same as for
    :class:`~openquake.hazardlib.source.point.PointSource`.
    """
    code = b'A'
    MODIFICATIONS = set()

    def __init__(self, source_id, name, tectonic_region_type,
                 mfd, rupture_mesh_spacing,
                 magnitude_scaling_relationship, rupture_aspect_ratio,
                 temporal_occurrence_model,
                 # point-specific parameters (excluding location)
                 upper_seismogenic_depth, lower_seismogenic_depth,
                 nodal_plane_distribution, hypocenter_distribution,
                 # area-specific parameters
                 polygon, area_discretization):
        super().__init__(
            source_id, name, tectonic_region_type, mfd, rupture_mesh_spacing,
            magnitude_scaling_relationship, rupture_aspect_ratio,
            temporal_occurrence_model)
        self.upper_seismogenic_depth = upper_seismogenic_depth
        self.lower_seismogenic_depth = lower_seismogenic_depth
        self.nodal_plane_distribution = nodal_plane_distribution
        self.hypocenter_distribution = hypocenter_distribution
        self.polygon = polygon
        self.area_discretization = area_discretization
        self.max_radius = 0

[docs]    def iter_ruptures(self, **kwargs):
        """
        See :meth:
        `openquake.hazardlib.source.base.BaseSeismicSource.iter_ruptures`
        for description of parameters and return value.

        Area sources are treated as a collection of point sources
        (see :mod:`openquake.hazardlib.source.point`) with uniform parameters.
        Ruptures of area source are just a union of ruptures
        of those point sources. The actual positions of the implied
        point sources form a uniformly spaced mesh on the polygon.
        Polygon's method :meth:
        `~openquake.hazardlib.geo.polygon.Polygon.discretize`
        is used for creating a mesh of points on the source's area.
        Constructor's parameter ``area_discretization`` is used as
        polygon's discretization spacing (not to be confused with
        rupture surface's mesh spacing which is as well provided
        to the constructor).

        The ruptures' occurrence rates are rescaled with respect to number
        of points the polygon discretizes to.
        """
        for src in self:
            yield from src.iter_ruptures(**kwargs)

[docs]    def count_ruptures(self):
        """
        See
        :meth:`openquake.hazardlib.source.base.BaseSeismicSource.count_ruptures`
        for description of parameters and return value.
        """
        if self.num_ruptures:
            return self.num_ruptures
        polygon_mesh = self.polygon.discretize(self.area_discretization)
        return (len(polygon_mesh) *
                len(self.get_annual_occurrence_rates()) *
                len(self.nodal_plane_distribution.data) *
                len(self.hypocenter_distribution.data))

    def __iter__(self):
        """
        Split an area source into a generator of point sources.

        MFDs will be rescaled appropriately for the number of points in the
        area mesh.
        """
        mesh = self.polygon.discretize(self.area_discretization)
        num_points = len(mesh)
        area_mfd = self.mfd
        if isinstance(area_mfd, mfd.TruncatedGRMFD):
            new_mfd = mfd.TruncatedGRMFD(
                a_val=area_mfd.a_val - math.log10(num_points),
                b_val=area_mfd.b_val,
                bin_width=area_mfd.bin_width,
                min_mag=area_mfd.min_mag,
                max_mag=area_mfd.max_mag)
        elif isinstance(area_mfd, mfd.EvenlyDiscretizedMFD):
            new_occur_rates = [x/num_points for x in area_mfd.occurrence_rates]
            new_mfd = mfd.EvenlyDiscretizedMFD(
                min_mag=area_mfd.min_mag,
                bin_width=area_mfd.bin_width,
                occurrence_rates=new_occur_rates)
        elif isinstance(area_mfd, mfd.ArbitraryMFD):
            new_occur_rates = [x/num_points for x in area_mfd.occurrence_rates]
            new_mfd = mfd.ArbitraryMFD(
                magnitudes=area_mfd.magnitudes,
                occurrence_rates=new_occur_rates)
        elif isinstance(area_mfd, mfd.YoungsCoppersmith1985MFD):
            new_mfd = mfd.YoungsCoppersmith1985MFD.from_characteristic_rate(
                area_mfd.min_mag, area_mfd.b_val, area_mfd.char_mag,
                area_mfd.char_rate / num_points, area_mfd.bin_width)
        else:
            raise TypeError('Unknown MFD: %s' % area_mfd)
        for i, (lon, lat) in enumerate(zip(mesh.lons, mesh.lats)):
            pt = PointSource(
                # Generate a new ID and name
                source_id='%s:%s' % (self.source_id, i),
                name=self.name,
                tectonic_region_type=self.tectonic_region_type,
                mfd=new_mfd,
                rupture_mesh_spacing=self.rupture_mesh_spacing,
                magnitude_scaling_relationship=
                self.magnitude_scaling_relationship,
                rupture_aspect_ratio=self.rupture_aspect_ratio,
                upper_seismogenic_depth=self.upper_seismogenic_depth,
                lower_seismogenic_depth=self.lower_seismogenic_depth,
                location=geo.Point(lon, lat),
                nodal_plane_distribution=self.nodal_plane_distribution,
                hypocenter_distribution=self.hypocenter_distribution,
                temporal_occurrence_model=self.temporal_occurrence_model)
            pt.num_ruptures = pt.count_ruptures()
            yield pt

[docs]    def wkt(self):
        """
        :returns: the geometry as a WKT string
        """
        return self.polygon.wkt