Temporal occurrence models¶
Module openquake.hazardlib.tom
contains implementations of probability
density functions for earthquake temporal occurrence modeling.

class
openquake.hazardlib.tom.
PoissonTOM
(time_span)[source]¶ Poissonian temporal occurrence model.
Parameters: time_span – The time interval of interest, in years. Raises: ValueError – If time_span
is not positive.
get_probability_no_exceedance
(occurrence_rate, poes)[source]¶ Compute and return, for a number of ground motion levels and sites, the probability that a rupture with annual occurrence rate given by
occurrence_rate
and able to cause ground motion values higher than a given level at a site with probabilitypoes
, does not cause any exceedance in the time window specified by thetime_span
parameter given in the constructor.The probability is computed using the following formula
(1  e ** (occurrence_rate * time_span)) ** poes
Parameters:  occurrence_rate – The average number of events per year.
 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
.
Returns: 2D numpy array containing probabilities of no exceedance. First dimension represents sites, second dimensions intensity measure levels.

get_probability_one_occurrence
(occurrence_rate)[source]¶ Calculate and return the probability of event to occur once within the time range defined by the constructor’s
time_span
parameter value.

get_probability_one_or_more_occurrences
(occurrence_rate)[source]¶ Calculate and return the probability of event to happen one or more times within the time range defined by constructor’s
time_span
parameter value.Calculates probability as
1  e ** (occurrence_rate*time_span)
.Parameters: occurrence_rate – The average number of events per year. Returns: Float value between 0 and 1 inclusive.

sample_number_of_occurrences
(occurrence_rate)[source]¶ Draw a random sample from the distribution and return a number of events to occur.
Method uses numpy random generator, which needs to be seeded outside of this method in order to get reproducible results.
Parameters: occurrence_rate – The average number of events per year. Returns: Sampled integer number of events to occur within model’s time span.
