“One of Oklahoma’s biggest man-made earthquakes, caused by fracking-linked wastewater injection, triggered an earthquake cascade that led to the damaging magnitude-5.7 Prague quake that struck on Nov. 6, 2011, a new study confirms.
“Even if wastewater injection only directly affects a low-hazard fault, those smaller events could trigger an event on a larger fault nearby,” she told Live Science.
The Prague earthquake was the largest of thousands of quakes that rattled Oklahoma in late 2011. Three were magnitude-5 or stronger. The 2011 quakes struck along the Wilzetta fault, a fault zone near Prague. Earthquakes break faults like a boat plowing through thick ice — the fault zips open as the earthquake ruptures the fault, and then seals itself shut behind. Each of the three biggest quakes tore apart a different part of the Wilzetta fault, the researchers said. [Image Gallery: Deadly Earthquakes]
Triggered foreshock
The magnitude-5.7 earthquake near Prague was preceded by a 5.0 quake that hit a day earlier, on Nov. 5. This “foreshock” occurred near an active wastewater disposal well. Thewastewater injection triggered the Nov. 5 earthquake, researchers concluded in a study published in March 2013 in the journal Geology. However, the Nov. 6 earthquake was farther from the wells….”
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