Good news the system being built for California, Oregon and Washington detects an earthquake is occurring and sends out alerts that may give warnings of few seconds to perhaps a minute before shaking arrives at locations away from the epicenter. The alerts are ready to be used more broadly, but not for mass public notification.
For more info, please read the original article by Mercury News:
https://www.mercurynews.com/2018/10/17/earthquake-warning-system-is-in-operational-mode/
