What to know about ‘doublet’ earthquakes like the destructive pair that hit Venezuela The U.S. Geological Survey has described the pair of earthquakes — a 7.1-magnitude and a 7.5-magnitude — as a doublet sequence, a phenomenon in which two temblors of similar magnitude strike roughly the same area at around the same time. The first earthquake “will probably have weakened some buildings or structures,” Tobin said. “Then collapses would happen during the second earthquake, even if they made it through the first one.” A 7.5-magnitude temblor is about three times bigger than a 7.1, since the Richter scale is logarithmic. https://www.nbcnews.com/science/earthquakes/venezuela-doublet-earthquakes-rcna351799
