# The Hazard Library
# Copyright (C) 2012-2019 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.base` defines a base class for
seismic sources.
"""
import abc
import math
import numpy
from openquake.baselib.slots import with_slots
[docs]@with_slots
class BaseSeismicSource(metaclass=abc.ABCMeta):
"""
Base class representing a seismic source, that is a structure generating
earthquake ruptures.
:param source_id:
Some (numeric or literal) source identifier. Supposed to be unique
within the source model.
:param name:
String, a human-readable name of the source.
:param tectonic_region_type:
Source's tectonic regime. See :class:`openquake.hazardlib.const.TRT`.
"""
_slots_ = ['source_id', 'name', 'tectonic_region_type',
'src_group_id', 'num_ruptures', 'id', 'min_mag']
RUPTURE_WEIGHT = 1. # overridden in (Multi)PointSource, AreaSource
ngsims = 1
min_mag = 0 # set in get_oqparams and CompositeSourceModel.filter
splittable = True
@abc.abstractproperty
def MODIFICATIONS(self):
pass
@property
def weight(self):
"""
Determine the source weight from the number of ruptures, by
multiplying with the scale factor RUPTURE_WEIGHT
"""
if not self.num_ruptures:
self.num_ruptures = self.count_ruptures()
# (MS) the weight is proportional to the number of ruptures and GSIMs
# the relation to the number of sites is unclear, but for sure less
# than linear and I am using a sqrt here (totally made up but good)
return (self.num_ruptures * self.RUPTURE_WEIGHT *
math.sqrt(self.nsites) * self.ngsims)
@property
def nsites(self):
"""
:returns: the number of sites affected by this source
"""
try:
# the engine sets self.indices when filtering the sources
return len(self.indices)
except AttributeError:
# this happens in several hazardlib tests, therefore we return
# a fake number of affected sites to avoid changing all tests
return 1
@property
def src_group_ids(self):
"""
:returns: a list of source group IDs (usually of 1 element)
"""
grp_id = getattr(self, 'src_group_id', [0])
return [grp_id] if isinstance(grp_id, int) else grp_id
def __init__(self, source_id, name, tectonic_region_type):
self.source_id = source_id
self.name = name
self.tectonic_region_type = tectonic_region_type
self.src_group_id = 0 # set by the engine
self.num_ruptures = 0 # set by the engine
self.seed = None # set by the engine
self.id = None # set by the engine
[docs] @abc.abstractmethod
def iter_ruptures(self):
"""
Get a generator object that yields probabilistic ruptures the source
consists of.
:returns:
Generator of instances of sublclass of :class:
`~openquake.hazardlib.source.rupture.BaseProbabilisticRupture`.
"""
[docs] def sample_ruptures(self, eff_num_ses, ir_monitor):
"""
:param eff_num_ses: number of stochastic event sets * number of samples
:param ir_monitor: a monitor object for .iter_ruptures()
:yields: pairs (rupture, num_occurrences[num_samples])
"""
mutex_weight = getattr(self, 'mutex_weight', 1)
with ir_monitor:
ruptures = list(self.iter_ruptures())
tom = getattr(self, 'temporal_occurrence_model', None)
serials = numpy.arange(self.serial, self.serial + self.num_ruptures)
if tom: # time-independent source
rates = numpy.array([rup.occurrence_rate for rup in ruptures])
numpy.random.seed(self.serial)
occurs = numpy.random.poisson(rates * tom.time_span * eff_num_ses)
for rup, serial, num_occ in zip(ruptures, serials, occurs):
if num_occ:
rup.serial = serial # used as seed
yield rup, num_occ
else: # time-dependent source
for rup, serial in zip(ruptures, serials):
numpy.random.seed(serial)
occurs = rup.sample_number_of_occurrences(eff_num_ses)
if mutex_weight < 1:
# consider only the occurrencies below the mutex_weight
occurs *= (numpy.random.random(eff_num_ses) < mutex_weight)
num_occ = occurs.sum()
if num_occ:
rup.serial = serial # used as seed
yield rup, num_occ
[docs] @abc.abstractmethod
def get_one_rupture(self, rupture_mutex=False):
"""
Yields one random rupture from a source
"""
def __iter__(self):
"""
Override to implement source splitting
"""
yield self
[docs] @abc.abstractmethod
def count_ruptures(self):
"""
Return the number of ruptures that will be generated by the source.
"""
[docs] @abc.abstractmethod
def get_min_max_mag(self):
"""
Return minimum and maximum magnitudes of the ruptures generated
by the source.
"""
[docs] def modify(self, modification, parameters):
"""
Apply a single modificaton to the source parameters
Reflects the modification method and calls it passing ``parameters``
as keyword arguments.
Modifications can be applied one on top of another. The logic
of stacking modifications is up to a specific source implementation.
:param modification:
String name representing the type of modification.
:param parameters:
Dictionary of parameters needed for modification.
:raises ValueError:
If ``modification`` is missing from the attribute `MODIFICATIONS`.
"""
if modification not in self.MODIFICATIONS:
raise ValueError('Modification %s is not supported by %s' %
(modification, type(self).__name__))
meth = getattr(self, 'modify_%s' % modification)
meth(**parameters)
[docs]@with_slots
class ParametricSeismicSource(BaseSeismicSource, metaclass=abc.ABCMeta):
"""
Parametric Seismic Source generates earthquake ruptures from source
parameters, and associated probabilities of occurrence are defined through
a magnitude frequency distribution and a temporal occurrence model.
:param mfd:
Magnitude-Frequency distribution for the source.
See :mod:`openquake.hazardlib.mfd`.
:param rupture_mesh_spacing:
The desired distance between two adjacent points in source's
ruptures' mesh, in km. Mainly this parameter allows to balance
the trade-off between time needed to compute the :meth:`distance
<openquake.hazardlib.geo.surface.base.BaseSurface.get_min_distance>`
between the rupture surface and a site and the precision of that
computation.
:param magnitude_scaling_relationship:
Instance of subclass of
:class:`openquake.hazardlib.scalerel.base.BaseMSR` to
describe how does the area of the rupture depend on magnitude and rake.
:param rupture_aspect_ratio:
Float number representing how much source's ruptures are more wide
than tall. Aspect ratio of 1 means ruptures have square shape,
value below 1 means ruptures stretch vertically more than horizontally
and vice versa.
:param temporal_occurrence_model:
Instance of
:class:`openquake.hazardlib.tom.PoissonTOM` defining temporal
occurrence model for calculating rupture occurrence probabilities
:raises ValueError:
If either rupture aspect ratio or rupture mesh spacing is not positive
(if not None).
"""
_slots_ = BaseSeismicSource._slots_ + '''mfd rupture_mesh_spacing
magnitude_scaling_relationship rupture_aspect_ratio
temporal_occurrence_model'''.split()
def __init__(self, source_id, name, tectonic_region_type, mfd,
rupture_mesh_spacing, magnitude_scaling_relationship,
rupture_aspect_ratio, temporal_occurrence_model):
super().__init__(source_id, name, tectonic_region_type)
if rupture_mesh_spacing is not None and not rupture_mesh_spacing > 0:
raise ValueError('rupture mesh spacing must be positive')
if rupture_aspect_ratio is not None and not rupture_aspect_ratio > 0:
raise ValueError('rupture aspect ratio must be positive')
self.mfd = mfd
self.rupture_mesh_spacing = rupture_mesh_spacing
self.magnitude_scaling_relationship = magnitude_scaling_relationship
self.rupture_aspect_ratio = rupture_aspect_ratio
self.temporal_occurrence_model = temporal_occurrence_model
[docs] def get_annual_occurrence_rates(self, min_rate=0):
"""
Get a list of pairs "magnitude -- annual occurrence rate".
The list is taken from assigned MFD object
(see :meth:`openquake.hazardlib.mfd.base.BaseMFD.get_annual_occurrence_rates`)
with simple filtering by rate applied.
:param min_rate:
A non-negative value to filter magnitudes by minimum annual
occurrence rate. Only magnitudes with rates greater than that
are included in the result list.
:returns:
A list of two-item tuples -- magnitudes and occurrence rates.
"""
return [(mag, occ_rate)
for (mag, occ_rate) in self.mfd.get_annual_occurrence_rates()
if (min_rate is None or occ_rate > min_rate) and
mag >= self.min_mag]
[docs] def get_min_max_mag(self):
"""
Get the minimum and maximum magnitudes of the ruptures generated
by the source from the underlying MFD.
"""
min_mag, max_mag = self.mfd.get_min_max_mag()
return max(self.min_mag, min_mag), max_mag
def __repr__(self):
"""
String representation of a source, displaying the source class name
and the source id.
"""
return '<%s %s>' % (self.__class__.__name__, self.source_id)
[docs] def get_one_rupture(self, rupture_mutex=False):
"""
Yields one random rupture from a source
"""
# The Mutex case is admitted only for non-parametric ruptures
msg = 'Mutually exclusive ruptures are admitted only in case of'
msg += ' non-parametric sources'
assert (not rupture_mutex), msg
# Set random seed and get the number of ruptures
num_ruptures = self.count_ruptures()
numpy.random.seed(self.seed)
idx = numpy.random.choice(num_ruptures)
# NOTE Would be nice to have a method generating a rupture given two
# indexes, one for magnitude and one setting the position
for i, rup in enumerate(self.iter_ruptures()):
if i == idx:
if hasattr(self, 'serial'):
rup.serial = self.serial
rup.idx = idx
return rup