At 22:40 UTC on 4 April 2010 (15:40 local, Easter Sunday), a magnitude 7.2 earthquake nucleated near the Sierra El Mayor and Sierra Cucapah, south of Mexicali, and ruptured bilaterally across at least seven faults over about 120 km of the Gulf of California shear zone beneath the Colorado River delta. It was felt by an estimated 20 million people from the Sea of Cortez to Los Angeles, Las Vegas and Phoenix, one of the most widely-felt quakes in the modern history of the American south-west, yet it killed only 2 to 4 people, with roughly 100 to 233 injured and more than 35,000 displaced on the Mexican side.
The reason is exposure, not hazard: the rupture struck a thinly-populated delta of farmland and desert rather than a dense city, and the damage that mattered was to water and land rather than buildings. Violent shaking liquefied the saturated delta soils, buckling irrigation canals and flooding more than 80,000 acres of Mexicali Valley farmland, driving most of the ~US$1.15bn economic loss (~US$440m in the Mexicali Valley, ~US$90m in the Imperial Valley). Insured loss was negligible on both sides of the border, structurally so in Mexico and by choice in California, where only around 10% of homeowners carry earthquake cover, leaving one of the clearest natural experiments in the protection gap in this catalogue.