Civil and Environmental Engineering, Imperial College London
Doi
Abstract
Despite the wide use of probabilistic seismic hazard analysis (PSHA) for the evaluation of seismic hazard, some degree of confusion and misunderstanding exists regarding how the hazard calculations should be performed as well as how the hazard results should be interpreted. In this thesis, different aspects of PSHA that are commonly misunderstood, as well as some new developments, are investigated. To this end, a comprehensive case study PSHA for three cities in the United Arab Emirates is carried out. Previous publications present contradictory interpretations of the earthquake threat in this country, creating confusion regarding appropriate seismic design levels. The results of this PSHA confirm low hazard levels in most of the country (UBC97, Zone 0) that increase as one moves northwards (UBC97, Zone 1). Using the case study as a point of reference, the mechanics and implications of performing hazard disaggregation when using multiple ground-motion prediction equations (GMPEs) within a logic-tree framework are investigated. Logic-tree approaches receive significant attention as different ways of representing hazard results from logic trees are discussed as well as issues associated with the identification of hazard-dominating scenarios and how these may influence the definition of scenario spectra for the selection of ground-motion records for seismic design. The sensitivity of the hazard results to key parameters in PSHA such as: the minimum magnitude deemed to be of engineering significance; the activity parameters of seismic sources; the use of alternative GMPEs and the standard deviations associated with these models; and the allocation of weights to logic-tree branches is investigated. Furthermore, recently proposed alternatives to the specification of a minimum magnitude as the criteria for identifying non-damaging earthquakes are studied. Finally, correlations between the hazard results obtained in terms of spectral accelerations and hazard results in terms of peak ground velocity and spectral intensity are explored
