A re-evaluation of the seismic hazard for the Maltese Islands

Abstract

This thesis is organised into eight chapters to provide a comprehensive seismic hazard assessment of the Maltese Islands. Chapter 1 outlines the study's motivations, emphasising the need for an updated seismic hazard assessment due to increasing population and building density in Malta. It reviews prior research and contextualises the significance of this study for earthquake-resistant planning and design. Chapter 2 outlines the seismotectonic features and seismogenic sources in the Mediterranean, needed for the definition of seismic source zones. It also introduces the Malta Seismic Network and provides an overview of the seismic history of the Maltese Islands. Chapter 3 details the methodology for seismic hazard assessment, focusing on probabilistic seismic hazard analysis (PSHA). It explains the key concepts, steps involved, and the logic tree approach used to incorporate uncertainties in the analysis. Chapter 4 discusses the development of ground motion prediction equations (GMPEs) using ridge regression and neural networks. These equations are calibrated for the Central Mediterranean region and compared with established models to ensure accuracy. Chapter 5 explains the use of R-CRISIS and OpenQuake software for conducting PSHA. It details the input parameters, source models, and the incorporation of site effects to provide a thorough seismic hazard assessment. Chapter 6 presents the PSHA results at bedrock conditions, followed by Chapter 7 which analyses and discusses these results. This chapter compares findings from CRISIS and OpenQuake, evaluates them against previous studies, and contrasts results based on bedrock versus site conditions. Chapter 8 summarises the main findings and offers recommendations for future research based on the results obtained. Each chapter progressively builds towards a comprehensive evaluation of seismic risk for the Maltese Islands, integrating advanced methodologies and tools to inform safer construction and planning practices.