"Shaking in 5 seconds!" A Voluntary Smartphone-based Earthquake Early Warning System

Public earthquake early warning systems have the potential to reduce individual risk by warning people of an incoming tremor, but their development is hampered by costly infrastructure. Furthermore, users' understanding of such a service and their reactions to warnings remains poorly studied. The Earthquake Network app turns users' smartphones into motion detectors and provides rapid information about felt earthquakes in multiple countries. It offers an alternative without the need of dedicated infrastructure in the many regions unlikely to be covered by conventional early warning systems in the foreseeable future. We show here that it already provides an early warning service, including for damaging shaking levels and although warnings are appreciated and understood by users, only a fraction follow the "drop, cover and hold" advice.