hazardcurves

Hazard curves are graphical representations used in seismic hazard assessment to show the probability that ground-motion intensity at a site will exceed a given level. They are typically plotted with the intensity measure, such as peak ground acceleration or spectral acceleration, on the horizontal axis and the annual probability of exceedance on the vertical axis. In practice, curves may also be presented as the return period corresponding to different levels of ground motion, or as the probability of exceedance over a specified time window.

Hazard curves are produced within probabilistic seismic hazard analysis (PSHA). The curves are generated by integrating the contributions from all potential earthquakes in a region, across ranges of magnitudes and distances, and using ground-motion prediction equations to relate source characteristics to site intensity. Site effects and epistemic and aleatoric uncertainties are incorporated, often via multiple GMPEs and logic trees. The result is an estimate of the annual rate of exceedance for every ground-motion level, sometimes accompanied by uncertainty bounds.

Interpretation and use are central to engineering and risk assessment. The curve enables engineers to translate a design level of ground motion into a corresponding annual risk or return period, aiding code development, site-specific design, and risk management. Limitations include model dependency, data quality, and simplifications such as assuming a Poisson temporal process. Hazard curves must be interpreted with an awareness of the underlying uncertainties and the regional assumptions embedded in the PSHA.