Earthquake effects

This chapter focuses on the earthquake hazard, and more specifically on the sensitivity of seismic hazard to the local geological conditions. The first section is a rapid overview of the main physical phenomena controlling the seismic ground motion from the emission of seismic waves on the fault (the ‘source’) to their arrival at ground surface, including the crustal propagation effects (propagation at large depth over large distances) and the shallow propagation effects, also called ‘site effects’. The second section is devoted to the latter, which are separated in two different kinds, those associated to the surface topography, and those related to the subsurface structure. For each of the two kinds, a first subsection describes the main observations, a second summarises what is known about their physics, and the third presents an outline of the state-of-practice for their estimation. The third section describes how earthquake-induced effects can be renstituted by scenarios in view of risk mitigation strategies to increase the resilience of human communities.