1. The first thing that happens after we encounter an earthquake is to wonder if anyone else felt it. The need for group validation is widespread and happens for events that don't involve earthquakes as well.
If those in the tribe feel something, we're likely to as well. That's why people look around before they stand up to offer an ovation at the end of a concert. Why should it matter if any of these strangers felt the way you did about the event? Because it does. A lot. Social proof matters.
2. Organizations are busy evacuating buildings, even national monuments. Even though experience indicates that the most dangerous thing you can do is have tens of thousands of people run down the stairs, cram into the elevators and stand in the streets, we do it anyway. Why? Because people like to do something. Action, even ineffective action, is something societies seek out during times of uncertainty.