Probabilistic Seismic Hazard Analysis (PSHA)

PROBABILISTIC SEISMIC HAZARD ANALYSIS (PSHA)

Probabilistic Seismic Hazard Analysis (PSHA) provides a framework in which the uncertainties can be identified. Further, they are quantified, and combined in a rational manner to provide a more complex picture of the seismic hazard.

Four Steps in PSHA

The probabilistic seismic hazard analysis (PSHA) requires the following four steps.

1. Identification and characterization of earthquake sources.

2. Characterisation of temporal distribution of earthquake recurrence. 

3. Determination of grand motion.

4. Computation of probability of earthquake.

1. Identification and characteristics of earthquake sources

The probability distribution of potential rupture locations within the source must also be characterized.

In most cases, uniform probability distributions are assigned to each source zone, implying that earthquakes are equally likely to occur at any point within the source zone.

These distributions are then combined with the source geometry to obtain the corresponding probability distribution of source-to-site distance.

2. Characteristics of temporal distribution of earthquake recurrence

Next, the seismicity or temporal distribution of earthquake recurrence must be

The recurrence relationship may accommodate the maximum size earthquake. But it does not limit consideration to that earthquake.

3. Determination of ground motion

The ground motion produced at the site by earthquake in each source zone must be determined with the use of predictive relationships.

4. Computation of probability of earthquake

Finally, the uncertainties in earthquake location, earthquake size, and ground motion parameter prediction are combined to obtain the probability and to the mechanics of the probability computations (Fig. 5.8).