Verification and Sensitivity Analysis of Maximum Likelihood Estimation for Loviisa NPP Seismic Hazard

Abstract

Probabilistic seismic hazard analysis (PSHA) is used for estimating the risk of earthquakes to nuclear power plants. To achieve a required level of safety, the recurrence of earthquakes of different magnitudes has to be known. This is done by estimating the parameters a and b in the Gutenberg-Richter equation. The purpose of this work is to verify the use of maximum likelihood estimation (MLE) method in the estimation of earthquake recurrence in Finland and perform a sensitivity analysis for this method. The verification and the sensitivity analysis are performed by comparing the estimated values of parameters a and b. The least squares (LS) method is included for comparison. The verification gives results similar to those from previous studies for both of the used methods. For the sensitivity analysis, changing completeness times, minimum and maximum magnitude and the width of the magnitude bins is tested. Both of the methods seem to be the most sensitive to changing the minimum magnitude, but the lack of high-magnitude events and the incompleteness of the data from the smallest earthquakes increase the uncertainty of the estimation. At the end of this paper, parameters giving the most reliable results are suggested.