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 probability poes, does not cause any exceedance in the time window specified by the time_span parameter given in the constructor.

The probability is computed using the following formula

(1 - e ** (-occurrence_rate * time_span)) ** poes
  • 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 the method.

2D numpy array containing probabilities of no exceedance. First dimension represents sites, second dimensions intensity measure levels.


Calculate and return the probability of event to occur once within the time range defined by the constructor’s time_span parameter value.


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.

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.

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