The Facebook Safety Check tool will notify your friends so that they know you're OK after a major disaster.
In times of disaster or crisis, people turn to Facebook to check on loved ones and get updates.
During a major disaster, Safety Check will help you:
Let friends and family know you’re safe
Check on others in the affected area
Mark your friends as safe
When the tool is activated after a natural disaster and if you’re in the affected area, you’ll receive a Facebook notification asking if you’re safe.
Facebook will determine your location by looking at the city you have listed in your profile, your last location if you’ve opted in to the Nearby Friends product, and the city where you are using the internet.
If you’re safe, you can select “I’m Safe” and a notification and News Feed story will be generated with your update. Your friends can also mark you as safe."