Improving the assessment of seismic hazard in the North Sea

Student thesis: Doctoral Thesis

Abstract

The following PhD thesis provides a comprehensive reassessment of probabilistic seismic hazard assessment (PSHA) in the North Sea. PSHA provides probabilistic representations of the expected ground-shaking at sites of interest, which can be used to assess the seismic risk for structures located at (or proximal to) said sites. In the North Sea, the seismic risk for offshore infrastructure including (1) oil and gas platforms and (2) wind turbine facilities must be considered. The seismic risk of this offshore infrastructure is important to consider because certain levels of seismic damage can result in negative impacts upon (1) the environmental health of the North Sea, (2) the personal health of employees on or near the considered infrastructure and (3) the economic health of governments and corporations which are reliant upon this infrastructure. The most recent publicly available North Sea PSHA was undertaken by Bungum et al. (2000). Two decades have passed since this study, since which substantial developments in PSHA have been made, and additional North Sea ground-motion data has been collected. Furthermore, the 2001 Ekofisk earthquake was the first hydrocarbon production induced earthquake in the North Sea to have been deemed of engineering significance for platforms in the region, but was not considered within the Bungum et al. (2000) study. In this investigation, North Sea PSHA is reassessed in several ways. Firstly, a pre-existing ground-motion prediction equation (GMPE) which performs well in the North Sea is identified as a base model for a North Sea GMPE using an additional 20 years of ground motion records available since the Bungum et al. (2000) study. This base model GMPE is then improved incrementally through the constrainment of North Sea path and site effects using novel techniques. Following the development of this North Sea GMPE, the seismogenic source model of Bungum et al. (2000) is updated using an additional two decades of North Sea earthquake observations. The impact of the North Sea GMPE and the updated source model are evaluated using (1) macroseismic earthquake observations and (2) assessment of the seismic risk of offshore infrastructure in the region. The updated PSHA formulation developed within this investigation results in moderate but significant differences in the seismic risk for offshore infrastructure in the North Sea. These seismic risk estimates are potentially more appropriate than those computed using the Bungum et al. (2000) PSHA formulation due to the additional ground-motion data and the PSHA advancements available since the Bungum et al. (2000) PSHA study. Ultimately, the improved seismic hazard estimates potentially help to better assess the structural health of offshore North Sea infrastructure, and subsequently minimise the likelihood of levels of seismic damage which could be detrimental to the North Sea environment or the personnel and/or economies operating within the region.
Date of Award1 Oct 2021
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorJohn Douglas (Supervisor) & Zoe Shipton (Supervisor)

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