Facebook has introduced a new feature called ‘Safety Check’ once a natural disaster has occurred the tool is activated 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.
and if you’re in the affected area, you’ll receive a Facebook notification asking if you’re safe.
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. Facebook says if we get your location wrong, you can mark that you’re outside the affected area.