Neo-Deterministic Seismic Hazard Analysis for the United Kingdom: from regional scale to nuclear site-specific application

Abstract

In the UK, seismic hazard analysis (SHA) relies exclusively on ground motion prediction equations (GMPE) developed from foreign earthquake recordings. Using these GMPE requires them be suitably adjusted to the UK environment whilst managing challenges related to GMPE aleatory uncertainty. Obtaining UK-tailored earthquake ground motion predictions could be equally achieved by using ground motion simulation models (GMSM), using recent findings about the UK geophysical landscape. This thesis investigates in depth one GMSM which could supply realistic synthetic earthquake seismograms representative of the UK environment. The thesis starts with a review of methodologies for SHA, namely the Deterministic Seismic Hazard Analysis (DSHA) and Probabilistic Seismic Hazard Analysis (PSHA), their constitutive components and the challenges in the UK context. One technique, the Modal Summation (MS), a critical part of the Neo-Deterministic Seismic Hazard Analysis (NDSHA), could incorporate the knowledge of earthquake source and crustal properties currently available in the UK and supply synthetic earthquake seismograms tailored to the UK seismic and geophysical environment. The synthetic seismograms are first validated against instrumental and macroseismic intensity datasets associated to British earthquakes, using multiple ground motion parameters of engineering interest. The NDSHA is then applied at a regional scale to develop national seismic hazard maps expressed using selected ground motion parameters. A sensitivity analysis is conducted on different methodology parameters to understand the key drivers of seismic hazard. Based on the learnings at regional scale, the NDSHA is then applied at a local scale, focusing on the Hinkley Point C (HPC) nuclear site and adjusting the methodology to the UK seismic context. It is also shown how the NDSHA incorporates the site effects resulting from lateral and topographical heterogeneities at the site. This thesis shows that the MS technique can provide realistic synthetic seismograms representative of the UK seismological and geophysical properties. In doing so, the technique contributes to addressing some of the current limitations observed in the GMPE traditionally used in UK SHA studies. The NDSHA methodology is shown to be able to act complementary to the PSHA approach context by possibly capping seismic ground motions or providing useful insights on seismic hazard levels generated by earthquake scenarios compatible with the UK tectonics.

Date of Award	31 Dec 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Parthasarathi Mandal (Supervisor) & Domenico Lombardi (Supervisor)