Earthquake early warning: Recent advances and perspectives

Earthquake early warning (EEW) is a relatively new strategy for reducing disaster risk and increasing resilience to seismic hazard in urban settings. EEW systems provide real-time information about ongoing earthquakes, enabling individuals, communities, governments, businesses and others located at distance to take timely action to reduce the probability of harm or loss before the earthquake-induced ground shaking reaches them. Examples of potential losses mitigated by EEW systems include injuries and infrastructure downtime. These systems are currently operating in nine countries, and are being/have been tested for implementation in 13 more. This paper reviews state-of-the-art approaches to EEW around the world. We specifically focus on the various algorithms that have been developed for the rapid calculation of seismic-source parameters, ground shaking, and potential consequences in the wake of an event. We also discuss limitations of the existing applied methodologies, with a particular emphasis on the lack of engineering-related (i.e., risk and resilience) metrics currently used to support decision-making related to the triggering of alerts by various end users. Finally, we provide a number of suggestions for future end-user-orientated advances in the field of EEW. For example, we propose that next-generation EEW systems should incorporate engineering-based, application-specific models/tools for more effective risk communication. They should operate within robust probabilistic frameworks that explicitly quantify uncertainties at each stage of the analysis, for more informed stakeholder decision-making. These types of advancements in EEW systems would represent an important paradigm shift in current approaches to issuing early warnings for natural hazards.