Earthquake early warning: Concepts, methods and physical grounds

Modern technology allows real-time seismic monitoring facilities to evolve into earthquake early warning (EEW) systems, capable of reducing deaths, injuries, and economic losses, as well as of speeding up rescue response and damage recovery. The objective of an EEW system is to estimate in a fast and reliable way the earthquake’s damage potential, before the strong shaking hits a given target. The necessary framework for EEW implementation is provided by the observed relationships between different parameters measured on the signal onsets and the final earthquake size. The implication of these observations on the physics of fracture processes has given rise to a significant debate in the seismological community. Currently, EEW systems are implemented or under testing in many countries of the world, and different methodologies and procedures have been studied and developed. The leading experience of countries like Japan or Mexico shows that, with a proper education of population and end-users, and with the design of real-time systems for the reduction of vulnerability/exposure, EEW can be an effective approach to the mitigation of the seismic risk at short time-scales.