India, May 2 -- Mexico City is sinking by nearly 10 inches (about 25 cm) a year, according to new satellite imagery released this week by NASA, making it one of the fastest-subsiding megacities in the world.

Spanning roughly 3,000 square miles (7,800 sq km), the metropolitan region is home to around 22 million people. The findings highlight the capabilities of the NISAR satellite (NASA-ISRO Synthetic Aperture Radar), which can track real-time changes in Earth's surface from orbit, even through cloud cover and dense vegetation.

According to NASA, the city is built atop an aquifer, and decades of excessive groundwater extraction-combined with the sheer weight of urban development-have led to the gradual compaction of the ancient lakebed b...