Earthquake Early Warning in Central America from 2016 to 2024

Abstract Earthquake early warning (EEW) systems that deliver real-time alerts to the public are now operating in Guatemala, El Salvador, Nicaragua, and Costa Rica. An independent system is operated by national seismological agencies in each country. The EEW systems were developed through the Alerta Temprana de Terremotos en América Central (ATTAC) project, a multi-year collaboration (2016–2024) led by ETH Zurich and funded by the Swiss Development Agency. These landmark systems are unique as they provide operational EEW in several low- and middle-income countries. Each system uses the same ETHZ-SED SeisComP EEW software that implements the virtual seismologist (VS) and finite-fault rupture detector (FinDer) algorithms. The national seismic monitoring infrastructures are supported by 72 EEW-ready strong-motion stations. Public alerts are disseminated primarily via a mobile application that has over one million users. EEW performance is regionally consistent due to shared real-time seismic data and common system architecture. Our evaluation period started when the software was installed and included periods of network and software optimization. The VS algorithm achieved an overall accuracy of 89%. Including FinDer reduced accuracy to 77%, mainly due to false positives in Nicaragua and Costa Rica that occurred early in the evaluation window. First alerts are generally available 10 s after origin time for shallow onshore events, with location and magnitude errors typically below 30 km and 0.5 units, respectively. Mobile alerting has proven effective in providing low-latency alerts to increasingly large numbers of users, with most users receiving red alerts within 2–8 s after issuance, though some variability can occur. Maintaining and enhancing EEW in the region requires sustained investment in seismic infrastructure, trained personnel, and dissemination solutions that, for the short term at least, will include the mobile application. Long-term viability depends on stable governance, consistent funding, and strengthened and coordinated public guidance on how to respond to alerts.