WASHINGTON - As many as 18,000 people dead. More than $250 billion in damages. Hundreds of thousands of people left homeless. That's not the latest estimate of Hurricane Katrina's toll on the Gulf Coast. That's a worst-case scenario if a major earthquake were to hit Los Angeles. The figures are hypothetical, from a model published in May by government researchers studying the Puente Hills fault under the city. Scientists warn that there's little doubt a major quake will hit California in coming years or decades, though many scenarios are not as disastrous as Puente Hills. As was the case with...