One key local SF Bay Area agency partnering for Earthquake Early Warning is BART, they operate the mass transit (partially underground, and have a tunnel under

One key local SF Bay Area agency partnering for Earthquake Early Warning is BART, they operate the mass transit (partially underground, and have a tunnel under the Bay Bridge, and more tunneling under construction to connect to San Jose Diridon) https://www.bart.gov/guide/safety/earthquake https://www.bart.gov/guide/safety/earthquake Early Warning Earthquake System BART is an early adopter of the ShakeAlert Earthquake Early Warning System. It has been in place at BART since August 2012 and in 2017 we upgraded to the new ShakeAlert 2.0 system. There are two servers receiving a continuous stream of messages from more than one hundred seismic stations located throughout Northern California. It receives actual shaking data from each seismic station once per second. The BART server calculates the earthquake's seismic intensity within nanoseconds, and if the seismic intensity -- or MMI (Modified Mercalli Intensity Scale) -- is greater than IV, the server will automatically signal trains to reduce speeds. Trains then automatically begin slowing to 27 mph. It takes about 20 seconds for trains in Automatic Train Operation at 70 mph to slow to 27 mph. This system removes human response time and can even slow trains down before the shaking occurs depending on how far away the quake is centered. Early warning depends on where the earthquake occurs. The farther away the shaking occurs, the more advance warning we get. The system can provide as as much as a 50 seconds early warning for earthquakes at or beyond extremes of the monitored region. For quakes centered within the BART region, there is no early warning but the system has the advantage of automated response to slow the trains instead of requiring human reaction. In 2020, BART and US Geographic Survey extended its agreement for BART to continue to use ShakeAlert data. 09-27-2012 "BART teams with UC Berkeley to adopt earthquake early warning system" https://www.bart.gov/news/articles/2012/news20120927 https://www.bart.gov/news/articles/2012/news20120927