Scientists and engineers from the California Institute of Technology (Caltech), U.S. Geological Survey in Pasadena, UC Berkeley and others around the world have been working on early warning systems to save lives during earthquakes.
Sensors detected the Napa quake 10 seconds before it struck.
About 1,000 sensors are placed about 50 miles apart in California, but Caltech scientists say more are needed for accurate early warnings.
Sensor locations include Paso Robles and Santa Barbara.
Certified emergency managers said they received a warning about the Napa quake within three minutes.
They said Caltech is still studying the results.
Santa Barbara County is currently a volunteer beta tester.
Engineers hope to roll out a notification system that will alert residents without a middleman.
It will take an estimated $100 million to finish the project.
Engineers hope to partner with business and industry to cover some of the costs.