# Nomogram to estimate the impact of epistemic uncertainty in the median earthquake ground motion on the hazard curve

Nomogram showing the effect of epistemic uncertainty in the earthquake ground motion model on the seismic hazard. The nomogram is developed using the approximate result of Toro (2006) connecting R, the ratio of the mean to median ground motion (e.g. peak ground acceleration) for a given annual frequency of exceedance, k, the slope of the hazard curve in log-log space, and sigma_mu, the lognormal epistemic uncertainty in the median ground motion (expressed as the standard deviation of the predicted median ground motions for a given magnitude and distance).

The isopleths show two example calculations using this graph by connecting with straight lines choices of k and sigma_mu and reading off the value of R.

See Douglas (Capturing Geographically-Varying Uncertainty in Earthquake Ground Motion Models or What We Think We Know May Change, doi: 10.1007/978-3-319-75741-4_6, 2018) for more details. The equation captured in this nomogram is Equation 6.1 of this paper (also see Table 6.1 of the same paper).

This nomogram was produced using Pynomo using a Type 2 equation.