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There's been a 4.6 aftershock this hour in the desert 16 miles southeast of Ocotillo, Calif., making at least ten earthquakes of magnitude 4 or higher today —including a pair of 5.1's. It's all playing out as expected after Sunday's 7.2 magnitude quake in Baja California south of Mexicali, Lucy Jones of the U.S. Geological Survey said earlier today on Patt Morrison's show on KPCC.
"Every earthquake makes another earthquake more likely," Jones reminded listeners. The region south of the Salton Sea is where the Pacific plate meets the North American plate in a jumble of faults, and the fault suspected in Sunday's quake broke off a 7-ish quake in 1892. The human toll has been less than in Haiti or Northridge or Loma Prieta — all smaller quakes — because this one began to rupture under the desert. "It didn't have many people really nearby...even Mexicali is at least 20 or 30 miles away," Jones said. "Proximity is 90 percent of the game when it comes to earthquake damage."
Scientists are pouring south to look for surface ruptures and gather data with their Mexican counterparts, Jones said. It's a curiosity as the largest quake in California or along the border since the 7.3 quake in Landers in 1992, as well as "the second largest earthquake of my career in Southern California....Everybody's mobilizing."
2005 photo of Lucy Jones via MSNBC