"I feel my heart start tremblin' whenever you're around"

The differences between East and West Coast 'quakes. For example, thus: "In the east the underlying bedrock is pretty well-connected (like a concrete slab). Eastern earthquakes can travel farther that in the west, where the underlying topography is so chopped-up (like a brick patio) that the energy of a quake is dissipated closer to the epicenter." 


That last might explain why it felt stronger than the readings would suggest.