The shaking woke Thomas Heaton on a quiet winter morning in Pasadena, California. The streets were empty, with sunrise hours away. As Heaton lay in bed next to his wife, waves vibrated through their house. Ten seconds. Fifteen. Twenty. As a seismologist, Heaton had spent his career studying seismic waves like these. By feel and duration, he guessed this quake was big, maybe a magnitude 6.5, and close, under west Los Angeles. Plenty dangerous. An aftershock rolled through.