Which statement best describes probabilistic seismic hazard assessment (PSHA)?

Which statement best describes probabilistic seismic hazard assessment (PSHA)?

• A. It predicts the exact year a fault will slip.
• B. It yields a single deterministic ground shaking value for a site.
• C. It only uses historical earthquakes without considering uncertainty.
• D. It estimates the likelihood of different ground motion levels at a site over a time frame.

Answer: (D)

Probabilistic seismic hazard assessment combines how often earthquakes of different sizes and locations occur with how those earthquakes would shake a site. For every possible earthquake scenario, it estimates the probability that ground motion will exceed a given level within a specified time window, and then sums over all scenarios to produce a hazard curve. This approach expresses hazard as probabilities over time and accounts for uncertainties in earthquake recurrence, source characteristics, and how ground shaking attenuates with distance. It does not try to predict an exact year for a quake and it goes beyond historical events by incorporating a range of possible events and their likelihoods.

Probabilistic seismic hazard assessment combines how often earthquakes of different sizes and locations occur with how those earthquakes would shake a site. For every possible earthquake scenario, it estimates the probability that ground motion will exceed a given level within a specified time window, and then sums over all scenarios to produce a hazard curve. This approach expresses hazard as probabilities over time and accounts for uncertainties in earthquake recurrence, source characteristics, and how ground shaking attenuates with distance. It does not try to predict an exact year for a quake and it goes beyond historical events by incorporating a range of possible events and their likelihoods.