ShakeAlert

ShakeAlert. It is an earthquake early warning system designed to provide seconds to tens of seconds of advance notice before strong shaking from a significant earthquake arrives. The system was developed through a collaborative partnership led by the United States Geological Survey alongside major research institutions including the California Institute of Technology, the University of California, Berkeley, the University of Washington, and the University of Oregon. Operational along the West Coast of the United States, it leverages a dense network of seismometers to detect the initial seismic waves and rapidly estimate the earthquake's location, magnitude, and potential shaking intensity.

Overview

The primary purpose of the system is to mitigate the impacts of damaging earthquakes by providing timely alerts to populations, critical infrastructure, and automated systems. It operates in regions of high seismic hazard, particularly in California, Oregon, and Washington, which are threatened by faults like the San Andreas Fault and the Cascadia subduction zone. Unlike a prediction tool, it functions as a rapid detection and notification system that capitalizes on the speed difference between fast-moving but harmless P-waves and the slower, destructive S-waves and surface waves. The initiative represents a significant advancement in applied seismology and public safety for the United States.

Development and implementation

The foundational research and prototyping for the system began in the early 2000s, influenced by successful international systems like Japan's Earthquake Early Warning system and Mexico's SASMEX. A major pilot program, supported by funding from the Gordon and Betty Moore Foundation, was launched in California in 2012. The Earthquake Hazards Program of the United States Geological Survey coordinated the multi-institutional effort to expand sensor coverage and develop robust algorithms. Following extensive testing, public alerting began in California in 2019 via integration with the Wireless Emergency Alerts system and mobile apps, with subsequent rollouts in Oregon and Washington.

Technology and operation

The technological backbone consists of a network of over 1,100 high-quality seismometers, part of the Advanced National Seismic System, that continuously transmit data to processing centers. Sophisticated algorithms, such as the ElarmS and FinDer systems, analyze the initial P-wave data in real-time to estimate the epicenter, magnitude, and expected shaking intensity. This processing occurs within seconds at data centers managed by the California Institute of Technology, the University of California, Berkeley, and the University of Washington. The system then disseminates alerts through various pathways before the arrival of stronger S-waves, with speed and accuracy being paramount to its utility.

Public alerts and response

Public notifications are delivered through several channels, including the federal Integrated Public Alert and Warning System, smartphone apps like MyShake, and partnerships with local entities such as the Los Angeles County and the City and County of San Francisco. These alerts provide critical seconds for individuals to enact protective actions like "Drop, Cover, and Hold On," and for automated systems to initiate pre-programmed responses. For example, the Bay Area Rapid Transit system can slow or stop trains, while hospitals can halt delicate surgeries. Public education campaigns, often coordinated with the Federal Emergency Management Agency, emphasize the brief nature of the warning and the importance of a practiced response.

Performance and effectiveness

The system's performance is evaluated based on the accuracy of its magnitude and location estimates, the speed of alert generation, and the reduction in false or missed alerts. It has been successfully triggered during notable events, such as the 2022 Ferndale earthquake. Its effectiveness in reducing injuries and economic loss is a subject of ongoing study by organizations like the Pacific Earthquake Engineering Research Center. Challenges remain in providing sufficient warning for areas very close to an epicenter, known as the "blind zone," and in ensuring alert delivery latency is minimized across all communication technologies.

Future developments

Future enhancements focus on increasing the density and robustness of the seismic network, particularly in the Pacific Northwest, and refining algorithms to improve speed and reduce magnitude underestimation for very large events like those on the Cascadia subduction zone. Research is also directed toward better estimating ground shaking in complex geological settings. Efforts are underway to expand integration with more infrastructure control systems, industrial facilities, and public warning systems, and to foster broader public preparedness initiatives in collaboration with state offices of emergency services.