Hurricane Katrina's devastating strike on New Orleans last fall highlighted shortcomings in the city's levee system. It also focused attention another long-term problem: The city and the region around it are sinking. New research suggests, however, that at least for nearby Michoud, La., the dominant driver pulling the region under may not be among the usual suspects: oil extraction, pumping groundwater to the surface, or diverting the Mississippi for navigation. Instead, the King of Slump may be a deep fault that cuts across southeastern Louisiana and under Michoud. During the 1970s, the fault appears to have contributed from 50 to...