Yes the alert gets sent to every cellphone user. Not just those who installed the ShakeAlert app. Whereas actually installing the ShakeAlert app helps improve c

Yes the alert gets sent to every cellphone user. Not just those who installed the ShakeAlert app. Whereas actually installing the ShakeAlert app helps improve crowdsourced early warnings on intensity and location. It is absolutely not necessary to install the ShakeAlert app to get the alerts. But it is a good civic-minded thing, and it does not compromise privacy.