Earthquake-resistant design can be considered as the art of balancing the seismic capacity of structures with the expected seismic demand to which they may be subjected. In this sense, earthquake-resistant design is the mitigation of seismic risk, which may be defined as the possibility of losses (human, social or economic) due to the effects of future earthquakes. Seismic risk is often considered as the convolution of seismic hazard, exposure and vulnerability. Exposure refers to the people, buildings, infrastructure, commercial and industrial facilities located in an area where earthquake effects may be felt; exposure is usually determined by planners and investors, although in some cases avoidance of major geo-hazards may lead to relocation of new infrastructure. Vulnerability is the susceptibility of structures to earthquake effects and is generally defined by the expected degree of damage that would result under different levels of seismic demand; this is the component of the risk equation that can be controlled by engineering design. Seismic hazards are the potentially damaging effects of earthquakes at a particular location, which may include surface rupture, tsunami
2.1 Introduction 7 2.2 Earthquake parameters and seismic source models 8 2.3 Ground-motion characterisation and prediction 12
2.3.1 Accelerograms: Recording and processing 12 2.3.2 Ground-motion parameters 13 2.3.3 Empirical ground-motion prediction equations 15 2.3.4 Ground-motion variability 17
2.4 Seismic hazard analysis 18 2.4.1 Probabilistic versus deterministic approaches 19 2.4.2 Basics of PSHA, hazard curves and return periods 19 2.4.3 Uncertainty and logic trees 23 2.4.4 Hazard maps and zonations 24
2.5 Elastic design response spectra 25 2.5.1 Uniform hazard spectra and code spectra 26 2.5.2 The influence of near-surface geology on response spectra 28 2.5.3 Displacement response spectra 30
2.6 Acceleration time-histories 33 2.7 Conclusions and recommendations 34 References 36
runup, liquefaction and landslides, although the most important cause of damage on a global scale is earthquake-induced ground shaking (Bird and Bommer, 2004). The focus in this chapter is exclusively on this particular hazard and the definition of seismic actions in terms of strong ground motions. In the context of probabilistic seismic hazard analysis (PSHA), seismic hazard actually refers to the probability of exceeding a specific level of ground shaking within a given window of time.