Announce a hard fork. /sarcasm  
To stop these crashes, we need whales to sell their coins to the new users who are becoming part of the whole economy because they may still possess some numbers that might cause some serious disaster in the price. As well, we should hold for long if we expect others too not to sell it. Bitcoin is not going to crash soon, though because there are some serious personalities taking place in this field who are not going to let it slip down that easy.