Probabilistic Seismic Hazard Analysis of A CO2 Storage Prospect Using the NGA East Ground Motion Models

Abstract

The Smeaheia fault block in the North Sea is a site under consideration for large scale CO2 storage. Even though the overall earthquake hazard in the North Sea is low, it is necessary to evaluate the risk related to earthquake hazard at the site to ensure safe storage of CO2 and to provide a baseline to be able to estimate the change in earthquake hazard due to future CO2 injection. This paper presents a probabilistic seismic hazard analysis (PSHA) for Smeaheia using an updated earthquake catalogue, two alternate source models and the final NGA East ground motion models. Defining the specific hazard related to the Vette and Øygarden faults, which bound the site, was not feasible due to a lack of data and uncertainty in earthquake location. However, by characterizing the main fault defining the continental-oceanic crust transition as an areal source zone, the results show that this zone dominates the earthquake hazard for the site. The results also show that the main earthquake scenarios that contribute to the hazard are magnitude 5 to 6 earthquakes 20 to 120 km from the site. The calculated peak ground accelerations (PGA) for 475 year and 2475 year return periods are 0.031 g and 0.088 g, respectively, which are smaller than in past studies.