Seismic sources and ruptures¶
Package openquake.hazardlib.source
deals with various types
of seismic sources.
Earthquake rupture¶
Module openquake.hazardlib.source.rupture
defines classes
Rupture
, BaseProbabilisticRupture
and its subclasses
NonParametricProbabilisticRupture
and
ParametricProbabilisticRupture

class
openquake.hazardlib.source.rupture.
BaseProbabilisticRupture
(mag, rake, tectonic_region_type, hypocenter, surface, source_typology, rupture_slip_direction=None, surface_nodes=())[source]¶ Base class for a probabilistic rupture, that is a
Rupture
associated with a temporal occurrence model defining probability of rupture occurrence in a certain time span.
get_probability_no_exceedance
(poes)[source]¶ Compute and return the probability that in the time span for which the rupture is defined, the rupture itself never generates a ground motion value higher than a given level at a given site.
Such calculation is performed starting from the conditional probability that an occurrence of the current rupture is producing a ground motion value higher than the level of interest at the site of interest.
The actual formula used for such calculation depends on the temporal occurrence model the rupture is associated with.
The calculation can be performed for multiple intensity measure levels and multiple sites in a vectorized fashion.
Parameters: poes – 2D numpy array containing conditional probabilities the the a rupture occurrence causes a ground shaking value exceeding a ground motion level at a site. First dimension represent sites, second dimension intensity measure levels. poes
can be obtained calling themethod
.

sample_number_of_occurrences
()[source]¶ Randomly sample number of occurrences from temporal occurrence model probability distribution.
Note
This method is using random numbers. In order to reproduce the same results numpy random numbers generator needs to be seeded, see http://docs.scipy.org/doc/numpy/reference/generated/numpy.random.seed.html
Returns: int, Number of rupture occurrences


class
openquake.hazardlib.source.rupture.
NonParametricProbabilisticRupture
(mag, rake, tectonic_region_type, hypocenter, surface, source_typology, pmf, rupture_slip_direction=None)[source]¶ Probabilistic rupture for which the probability distribution for rupture occurrence is described through a generic probability mass function.
Parameters: pmf – Instance of
openquake.hazardlib.pmf.PMF
. Values in the abscissae represent number of rupture occurrences (in increasing order, staring from 0) and values in the ordinates represent associated probabilities. Example: if, for a given time span, a rupture has probability0.8
to not occurr,0.15
to occur once, and0.05
to occur twice, thepmf
can be defined aspmf = PMF([(Decimal('0.8'), 0), (Decimal('0.15'), 1), Decimal('0.05', 2)])
Raises: ValueError – If number of ruptures in pmf
do not start from 0, are not defined in increasing order, and if they are not defined with unit step
get_probability_no_exceedance
(poes)[source]¶ See
superclass method
for spec of input and result values.Uses the formula
∑ p(kT) * p(X<xrup)^k
where
p(kT)
is the probability that the rupture occurs k times in the time spanT
,p(X<xrup)
is the probability that a rupture occurrence does not cause a ground motion exceedance, and the summation∑
is done over the number of occurrencesk
.p(kT)
is given by the constructor’s parameterpmf
, andp(X<xrup)
is computed as1  poes
.

sample_number_of_occurrences
()[source]¶ See
superclass method
for spec of input and result values.Uses ‘Inverse Transform Sampling’ method.


class
openquake.hazardlib.source.rupture.
ParametricProbabilisticRupture
(mag, rake, tectonic_region_type, hypocenter, surface, source_typology, occurrence_rate, temporal_occurrence_model, rupture_slip_direction=None)[source]¶ Rupture
associated with an occurrence rate and a temporal occurrence model.Parameters:  occurrence_rate – Number of times rupture happens per year.
 temporal_occurrence_model – Temporal occurrence model assigned for this rupture. Should
be an instance of
openquake.hazardlib.tom.PoissonTOM
.
Raises: ValueError – If occurrence rate is not positive.

get_cdppvalue
(target, buf=1.0, delta=0.01, space=2.0)[source]¶ Get the directivity prediction value, centred DPP(cdpp) at a given site as described in Spudich et al. (2013), and this cdpp is used in Chiou and Young(2014) GMPE for nearfault directivity term prediction.
Parameters:  target_site – A mesh object representing the location of the target sites.
 buf – A float vaule presents the buffer distance in km to extend the mesh borders to.
 delta – A float vaule presents the desired distance between two adjacent points in mesh
 space – A float vaule presents the tolerance for the same distance of the sites (default 2 km)
Returns: A float value presents the centreed directivity predication value which used in Chioud and Young(2014) GMPE for directivity term

get_dppvalue
(site)[source]¶ Get the directivity prediction value, DPP at a given site as described in Spudich et al. (2013).
Parameters: site – Point
object representing the location of the target siteReturns: A float number, directivity prediction value (DPP).

get_probability_no_exceedance
(poes)[source]¶ See
superclass method
for spec of input and result values.

get_probability_one_occurrence
()[source]¶ Return the probability of this rupture to occur exactly one time.
Uses :meth: ~openquake.hazardlib.tom.PoissonTOM.get_probability_one_occurrence of an assigned temporal occurrence model.

get_probability_one_or_more_occurrences
()[source]¶ Return the probability of this rupture to occur one or more times.
Uses
get_probability_one_or_more_occurrences()
of an assigned temporal occurrence model.

class
openquake.hazardlib.source.rupture.
Rupture
(mag, rake, tectonic_region_type, hypocenter, surface, source_typology, rupture_slip_direction=None, surface_nodes=())[source]¶ Rupture object represents a single earthquake rupture.
Parameters:  mag – Magnitude of the rupture.
 rake – Rake value of the rupture.
See
NodalPlane
.  tectonic_region_type – Rupture’s tectonic regime. One of constants
in
openquake.hazardlib.const.TRT
.  hypocenter – A
Point
, rupture’s hypocenter.  surface – An instance of subclass of
BaseSurface
. Object representing the rupture surface geometry.  source_typology – Subclass of
BaseSeismicSource
(class object, not an instance) referencing the typology of the source that produced this rupture.  rupture_slip_direction – Angle describing rupture propagation direction in decimal degrees.
Raises: ValueError – If magnitude value is not positive, hypocenter is above the earth surface or tectonic region type is unknown.
NB: if you want to convert the rupture into XML, you should set the attribute surface_nodes to an appropriate value.
Point source¶
Module openquake.hazardlib.source.point
defines PointSource
.

class
openquake.hazardlib.source.point.
PointSource
(source_id, name, tectonic_region_type, mfd, rupture_mesh_spacing, magnitude_scaling_relationship, rupture_aspect_ratio, temporal_occurrence_model, upper_seismogenic_depth, lower_seismogenic_depth, location, nodal_plane_distribution, hypocenter_distribution)[source]¶ Point source typology represents seismicity on a single geographical location.
Parameters:  upper_seismogenic_depth – Minimum depth an earthquake rupture can reach, in km.
 lower_seismogenic_depth – Maximum depth an earthquake rupture can reach, in km.
 location –
Point
object representing the location of the seismic source. The depth value of that point is ignored.  nodal_plane_distribution –
PMF
object with values that are instances ofopenquake.hazardlib.geo.nodalplane.NodalPlane
. Shows the distribution of probability for rupture to have the certain nodal plane.  hypocenter_distribution –
PMF
with values being float numbers in km representing the depth of the hypocenter. Latitude and longitude of the hypocenter is always set to ones oflocation
.
See also
openquake.hazardlib.source.base.ParametricSeismicSource
for description of other parameters.Raises: ValueError – If upper seismogenic depth is negative or below lower seismogenic depth, if one or more of hypocenter depth values is shallower than upper seismogenic depth or deeper than lower seismogenic depth. 
_get_max_rupture_projection_radius
()[source]¶ Find a maximum radius of a circle on Earth surface enveloping a rupture produced by this source.
Returns: Half of maximum rupture’s diagonal surface projection.

_get_rupture_dimensions
(mag, nodal_plane)[source]¶ Calculate and return the rupture length and width for given magnitude
mag
and nodal plane.Parameters: nodal_plane – Instance of openquake.hazardlib.geo.nodalplane.NodalPlane
.Returns: Tuple of two items: rupture length in width in km. The rupture area is calculated using method
get_median_area()
of source’s magnitudescaling relationship. In any case the returned dimensions multiplication is equal to that value. Than the area is decomposed to length and width with respect to source’s rupture aspect ratio.If calculated rupture width being inclined by nodal plane’s dip angle would not fit in between upper and lower seismogenic depth, the rupture width is shrunken to a maximum possible and rupture length is extended to preserve the same area.

_get_rupture_surface
(mag, nodal_plane, hypocenter)[source]¶ Create and return rupture surface object with given properties.
Parameters:  mag – Magnitude value, used to calculate rupture dimensions,
see
_get_rupture_dimensions()
.  nodal_plane – Instance of
openquake.hazardlib.geo.nodalplane.NodalPlane
describing the rupture orientation.  hypocenter – Point representing rupture’s hypocenter.
Returns: Instance of
PlanarSurface
. mag – Magnitude value, used to calculate rupture dimensions,
see

_iter_ruptures_at_location
(temporal_occurrence_model, location, rate_scaling_factor=1)[source]¶ The common part of :meth: openquake.hazardlib.source.point.Point.iter_ruptures shared between point source and
AreaSource
.Parameters:  temporal_occurrence_model – The same object as given to :meth: openquake.hazardlib.source.base.BaseSeismicSource.iter_ruptures.
 location – A
Point
object representing the hypocenter location. In case ofPointSource
it is the one provided to constructor, and for area source the location points are taken from polygon discretization.  rate_scaling_factor – Positive float number to multiply occurrence rates by. It is used
by area source to scale the occurrence rates with respect
to number of locations. Point sources use no scaling
(
rate_scaling_factor = 1
).

count_ruptures
()[source]¶ See :meth: openquake.hazardlib.source.base.BaseSeismicSource.count_ruptures.

filter_sites_by_distance_to_source
(integration_distance, sites)[source]¶ Filter sites that are closer than maximum rupture projection radius plus integration distance along the great circle arc from source’s epicenter location. Overrides
base class' method
in order to avoid using polygon.

get_rupture_enclosing_polygon
(dilation=0)[source]¶ Returns a circleshaped polygon with radius equal to
dilation
plus_get_max_rupture_projection_radius()
.See
superclass method
for parameter and return value definition.
Area source¶
Module openquake.hazardlib.source.area
defines AreaSource
.

class
openquake.hazardlib.source.area.
AreaSource
(source_id, name, tectonic_region_type, mfd, rupture_mesh_spacing, magnitude_scaling_relationship, rupture_aspect_ratio, temporal_occurrence_model, upper_seismogenic_depth, lower_seismogenic_depth, nodal_plane_distribution, hypocenter_distribution, polygon, area_discretization)[source]¶ Area source represents uniform seismicity occurring over a geographical region.
Parameters:  polygon – An instance of
openquake.hazardlib.geo.polygon.Polygon
that defines source’s area.  area_discretization – Float number, polygon area discretization spacing in kilometers.
See
openquake.hazardlib.source.area.AreaSource.iter_ruptures()
.
Other parameters (except
location
) are the same as forPointSource
.
count_ruptures
()[source]¶ See
openquake.hazardlib.source.base.BaseSeismicSource.count_ruptures()
for description of parameters and return value.

filter_sites_by_distance_to_source
(integration_distance, sites)[source]¶ Overrides
implementation
of the point source class just to call thebase class one
.

get_rupture_enclosing_polygon
(dilation=0)[source]¶ Extends the area source polygon by
dilation
plus_get_max_rupture_projection_radius()
.See
superclass method
for parameter and return value definition.

iter_ruptures
()[source]¶ See
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
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 parameterarea_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.
 polygon – An instance of
Simple fault¶
Module openquake.hazardlib.source.simple_fault
defines
SimpleFaultSource
.

class
openquake.hazardlib.source.simple_fault.
SimpleFaultSource
(source_id, name, tectonic_region_type, mfd, rupture_mesh_spacing, magnitude_scaling_relationship, rupture_aspect_ratio, temporal_occurrence_model, upper_seismogenic_depth, lower_seismogenic_depth, fault_trace, dip, rake, hypo_list=(), slip_list=())[source]¶ Simple fault source typology represents seismicity occurring on a fault surface with simple geometry.
Parameters:  upper_seismogenic_depth – Minimum depth an earthquake rupture can reach, in km.
 lower_seismogenic_depth – Maximum depth an earthquake rupture can reach, in km.
 fault_trace – A
Line
representing the line of intersection between the fault plane and the Earth’s surface.  dip – Angle between earth surface and fault plane in decimal degrees.
 rake – the direction of hanging wall relative to the foot wall.
 rupture_slip_direction – Angle describing rupture propagation direction in decimal degrees.
 hypo_list – Array describing the relative position of the hypocentre on the rupture surface. Each line represents a hypocentral position defined in terms of the relative distance along strike and dip (from the upper, left corner of the fault surface i.e. the corner which results from the projection at depth of the first vertex of the fault trace) and the corresponding weight. Example 1: one single hypocentral position at the center of the rupture will be described by the following array[(0.5, 0.5, 1.0)]. Example 2: two possible hypocenters are admitted for a rupture. One hypocentre is located along the strike at 1/4 of the fault length and at 1/4 of the fault width along the dip and occurs with a weight of 0.3, the other one is at 3/4 of fault length along strike and at 3/4 of fault width along strike with a weight of 0.7. The numpy array would be entered as numpy.array([[0.25, 0.25, 0.3], [0.75, 0.75, 0.7]]).
 slip_list – Array describing the rupture slip direction, which desribes the rupture propagation direction on the rupture surface. Each line represents a rupture slip direction and the corresponding weight. Example 1: one single rupture slip direction with angle 90 degree will be described by the following array[(90, 1.0)]. Example 2: two possible rupture slip directions are admitted for a rupture. One slip direction is at 90 degree with a weight of 0.7, the other one is at 135 degree with a weight of 0.3. The numpy array would be entered as numpy.array( [[90, 0.7], [135, 0.3]]).
See also
openquake.hazardlib.source.base.ParametricSeismicSource
for description of other parameters.Raises: ValueError – If check_fault_data()
fails, if rake value is invalid and if rupture mesh spacing is too high for the lowest magnitude value.
count_ruptures
()[source]¶ See :meth: openquake.hazardlib.source.base.BaseSeismicSource.count_ruptures.

get_rupture_enclosing_polygon
(dilation=0)[source]¶ Uses
openquake.hazardlib.geo.surface.simple_fault.SimpleFaultSurface.surface_projection_from_fault_data()
for getting the fault’s surface projection and then calls itsdilate()
method passing indilation
parameter.See
superclass method
for parameter and return value definition.

iter_ruptures
()[source]¶ See :meth: openquake.hazardlib.source.base.BaseSeismicSource.iter_ruptures.
Generates a ruptures using the “floating” algorithm: for all the magnitude values of assigned MFD calculates the rupture size with respect to MSR and aspect ratio and then places ruptures of that size on the surface of the whole fault source. The occurrence rate of each of those ruptures is the magnitude occurrence rate divided by the number of ruptures that can be placed in a fault.

modify_adjust_dip
(increment)[source]¶ Modifies the dip by an incremental value
Parameters: increment (float) – Value by which to increase or decrease the dip (the resulting dip must still be within 0.0 to 90.0 degrees)
Complex fault¶
Module openquake.hazardlib.source.complex_fault
defines ComplexFaultSource
.

class
openquake.hazardlib.source.complex_fault.
ComplexFaultSource
(source_id, name, tectonic_region_type, mfd, rupture_mesh_spacing, magnitude_scaling_relationship, rupture_aspect_ratio, temporal_occurrence_model, edges, rake)[source]¶ Complex fault source typology represents seismicity occurring on a fault surface with an arbitrarily complex geometry.
Parameters:  edges – A list of
Line
objects, representing fault source geometry. Seeopenquake.hazardlib.geo.surface.complex_fault.ComplexFaultSurface.from_fault_data()
.  rake – Angle describing rupture propagation direction in decimal degrees.
See also
openquake.hazardlib.source.base.ParametricSeismicSource
for description of other parameters.Raises: ValueError – If check_fault_data()
fails or if rake value is invalid.
count_ruptures
()[source]¶ See :meth: openquake.hazardlib.source.base.BaseSeismicSource.count_ruptures.

get_rupture_enclosing_polygon
(dilation=0)[source]¶ Uses
openquake.hazardlib.geo.surface.complex_fault.ComplexFaultSurface.surface_projection_from_fault_data()
for getting the fault’s surface projection and then calls itsdilate()
method passing indilation
parameter.See
superclass method
for parameter and return value definition.

iter_ruptures
()[source]¶ See :meth: openquake.hazardlib.source.base.BaseSeismicSource.iter_ruptures.
Uses
_float_ruptures()
for finding possible rupture locations on the whole fault surface.
 edges – A list of

openquake.hazardlib.source.complex_fault.
_float_ruptures
(rupture_area, rupture_length, cell_area, cell_length)[source]¶ Get all possible unique rupture placements on the fault surface.
Parameters:  rupture_area – The area of the rupture to float on the fault surface, in squared km.
 rupture_length – The target length (spatial extension along fault trace) of the rupture, in km.
 cell_area – 2d numpy array representing area of mesh cells in squared km.
 cell_length – 2d numpy array of the shape as
cell_area
representing cells’ length in km.
Returns: A list of slice objects. Number of items in the list is equal to number of possible locations of the requested rupture on the fault surface. Each slice can be used to get a portion of the whole fault surface mesh that would represent the location of the rupture.
Characteristic source¶
Module openquake.hazardlib.source.characteristic
defines
CharacteristicFaultSource
.

class
openquake.hazardlib.source.characteristic.
CharacteristicFaultSource
(source_id, name, tectonic_region_type, mfd, temporal_occurrence_model, surface, rake, surface_node=None)[source]¶ Characteristic source typology represents seismicity occuring on a generic fault surface with seismic events rupturing the entire fault surface independently of their magnitude values.
Characteristic source typology can be used to model individual faults or fault segments that tend to produce essentialy same size earthquakes (see for instance: Schwartz, D. P., K. J. Coppersmith, Fault behavior and characteristic earthquakes: Examples from the Wasatch and San Andreas fault zones, J. Geophys. Res., 89, 56815698, 1984)
Parameters:  surface – Fault surface, see
openquake.hazardlib.geo.surface
.  rake – Angle describing rupture propagation direction in decimal degrees.
See also
openquake.hazardlib.source.base.ParametricSeismicSource
for description of other parameters.Note that a
CharacteristicFaultSource
does not need any mesh spacing, magnitude scaling relationship, and aspect ratio, therefore the constructor sets these parameters toNone
.NB: if you want to convert a characteristic source into XML, you must set its attribute surface_node to an explicit representation of the surface as a LiteralNode object.

count_ruptures
()[source]¶ See :meth: openquake.hazardlib.source.base.BaseSeismicSource.count_ruptures.

get_rupture_enclosing_polygon
(dilation=0)[source]¶ Uses :meth: openquake.hazardlib.geo.surface.base.BaseSurface.get_bounding_box() and from bounding box coordinates create
openquake.hazardlib.geo.mesh.RectangularMesh
and then callsopenquake.hazardlib.geo.mesh.Mesh.get_convex_hull()
to get a polygon representation of the bounding box. Note that this is needed to cope with the situation of a vertical rupture for which the bounding box collapses to a line. In this case the methodget_convex_hull()
returns a valid polygon obtained by expanding the line by a small distance. Finally, a polygon is returned by callingdilate()
passing in thedilation
parameter.See
superclass method
for parameter and return value definition.

iter_ruptures
()[source]¶ See :meth: openquake.hazardlib.source.base.BaseSeismicSource.iter_ruptures.
For each magnitude value in the given MFD, return an earthquake rupture with a surface always equal to the given surface.

modify_set_geometry
(surface, surface_node=None)[source]¶ Modifies the current fault geometry
Parameters:  surface – Fault surface, see
openquake.hazardlib.geo.surface
.  surface_node – If needed for export, provide the surface as a LiteralNode object
 surface – Fault surface, see
 surface – Fault surface, see
Non Parametric source¶
Module openquake.hazardlib.source.non_parametric
defines
NonParametricSeismicSource

class
openquake.hazardlib.source.non_parametric.
NonParametricSeismicSource
(source_id, name, tectonic_region_type, data)[source]¶ Non Parametric Seismic Source explicitly defines earthquake ruptures in the constructor. That is earthquake ruptures are not generated algorithmically from a set of source parameters.
Ruptures’ rectonic region types are overwritten by source tectonic region type.
Parameters: data – List of tuples. Each tuple must contain two items. The first item must be an instance of openquake.hazardlib.source.rupture.Rupture
. The second item must be an instance ofopenquake.hazardlib.pmf.PMF
describing the probability of the rupture to occur N times (the PMF must be defined from a minimum number of occurrences equal to 0)
count_ruptures
()[source]¶ See :meth: openquake.hazardlib.source.base.BaseSeismicSource.count_ruptures.

get_min_max_mag
()[source]¶ Return the minimum and maximum magnitudes of the ruptures generated by the source

get_rupture_enclosing_polygon
(dilation=0)[source]¶ Create instance of
openquake.hazardlib.geo.surface.multi.MultiSurface
from all ruptures’ surfaces and compute its bounding box. Calculate convex hull of bounding box, and return it dilated bydilation
.Parameters: dilation – A buffer distance in km to extend the polygon borders to. Returns: Instance of openquake.hazardlib.geo.polygon.Polygon
.

Abstract base seismic source¶
Module openquake.hazardlib.source.base
defines a base class for
seismic sources.

class
openquake.hazardlib.source.base.
BaseSeismicSource
(source_id, name, tectonic_region_type)[source]¶ Base class representing a seismic source, that is a structure generating earthquake ruptures.
Parameters:  source_id – Some (numeric or literal) source identifier. Supposed to be unique within the source model.
 name – String, a humanreadable name of the source.
 tectonic_region_type – Source’s tectonic regime. See
openquake.hazardlib.const.TRT
.

filter_sites_by_distance_to_source
(integration_distance, sites)[source]¶ Filter out sites from the collection that are further from the source than some arbitrary threshold.
Parameters:  integration_distance – Distance in km representing a threshold: sites that are further than that distance from the closest rupture produced by the source should be excluded.
 sites – Instance of
openquake.hazardlib.site.SiteCollection
to filter.
Returns: Filtered
SiteCollection
.Method can be overridden by subclasses in order to achieve higher performance for a specific typology. Base class method calls
get_rupture_enclosing_polygon()
withintegration_distance
as a dilation value and then filters site collection by checking :meth: containment <openquake.hazardlib.geo.polygon.Polygon.intersects> of site locations.The main criteria for this method to decide whether a site should be filtered out or not is the minimum distance between the site and all the ruptures produced by the source. If at least one rupture is closer (in terms of great circle distance between surface projections) than integration distance to a site, it should not be filtered out. However, it is important not to make this method too computationally intensive. If shortcircuits are taken, false positives are generally better than false negatives (it’s better not to filter a site out if there is some uncertainty about its distance).

get_min_max_mag
()[source]¶ Return minimum and maximum magnitudes of the ruptures generated by the source.

get_rupture_enclosing_polygon
(dilation=0)[source]¶ Get a polygon which encloses all the ruptures generated by the source.
The rupture enclosing polygon is meant to be used in all hazard calculators to filter out sources whose ruptures the user wants to be neglected because they are too far from the locations of interest.
For performance reasons, the
get_rupture_enclosing_polygon()
should compute the polygon, without creating all the ruptures. The rupture enclosing polygon may not be necessarily the minimum enclosing polygon, but must guarantee that all ruptures are within the polygon.This method must be implemented by subclasses.
Parameters: dilation – A buffer distance in km to extend the polygon borders to. Returns: Instance of openquake.hazardlib.geo.polygon.Polygon
.

iter_ruptures
()[source]¶ 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.

modify
(modification, parameters)[source]¶ 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.
Parameters:  modification – String name representing the type of modification.
 parameters – Dictionary of parameters needed for modification.
Raises: ValueError – If
modification
is missing from the attribute MODIFICATIONS.

weight
¶ Determine the source weight from the number of ruptures, by multiplying with the scale factor RUPTURE_WEIGHT

class
openquake.hazardlib.source.base.
ParametricSeismicSource
(source_id, name, tectonic_region_type, mfd, rupture_mesh_spacing, magnitude_scaling_relationship, rupture_aspect_ratio, temporal_occurrence_model)[source]¶ 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.
Parameters:  mfd – MagnitudeFrequency distribution for the source.
See
openquake.hazardlib.mfd
.  rupture_mesh_spacing – The desired distance between two adjacent points in source’s
ruptures’ mesh, in km. Mainly this parameter allows to balance
the tradeoff between time needed to compute the
distance
between the rupture surface and a site and the precision of that computation.  magnitude_scaling_relationship – Instance of subclass of
openquake.hazardlib.scalerel.base.BaseMSR
to describe how does the area of the rupture depend on magnitude and rake.  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.
 temporal_occurrence_model – Instance of
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).

get_annual_occurrence_rates
(min_rate=0)[source]¶ Get a list of pairs “magnitude – annual occurrence rate”.
The list is taken from assigned MFD object (see
openquake.hazardlib.mfd.base.BaseMFD.get_annual_occurrence_rates()
) with simple filtering by rate applied.Parameters: min_rate – A nonnegative 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 twoitem tuples – magnitudes and occurrence rates.
 mfd – MagnitudeFrequency distribution for the source.
See