How the Nepal Earthquake Happened
Experts explain the science behind Saturday’s deadly earthquake A little before noon Saturday in Nepal, a chunk of rock 15 kilometers below the earth’s surface shifted , unleashing a shock wave—described as being as powerful as the explosion of more than 20 thermonuclear weapons—that ripped through the Katmandu Valley. In geological terms, the tremor occurred like clockwork—81 years after the region’s last earthquake of such a magnitude, in 1934. Historical records dating to 1255 indicate the region—known as the Indus-Yarlung suture zone—experiences a magnitude-8 earthquake “approximately every 75 years,” according to a report by Nepal’s National Society for Earthquake Technology. ‘Earthquakes dissipate energy, like lifting the lid off a pot of boiling water. But it builds back up after you put the lid back on.’ —Lung S. Chan, geophysicist at the University of Hong Kong The reason is the regular movement of the fault line that runs along Nepal’s southern border, where the Ind