Powerful radar system is providing new data on city’s subsidence, which experts hope will draw more attention to itWalking into Mexico City’s sprawling central Zócalo is a dizzying experience. At one end of the plaza, the capital’s cathedral, with its soaring spires, slumps in one direction. An attached church, known as the Metropolitan Sanctuary, tilts in the other. The nearby National Palace also seems off-kilter.The teetering of many of the capital’s historic buildings is the most visible sig...