Tectonic plates are under constant stress from their edges (ridge push and slab pull). In stable “cratons,” this stress usually does nothing. However, if there is an old scar in the crust, like the New Madrid Seismic Zone in the USA or the Kutch region in India, the stress concentrates there. Because the crust in these stable regions is cold and dense, seismic waves travel much further and with less energy loss than at plate boundaries. This is why intraplate quakes can be felt over thousands of kilometers and cause massive damage in areas not usually prepared for tremors.