Much of Oklahoma and the vicinity of Dallas, Texas, face the same earthquake risk this year as the fault-ridden areas of California, according to a 28 March study by the US Geological Survey. It is the first time the USGS has mapped the hazard from both natural and induced earthquakes. Past forecasts have included only natural earthquakes.
The main cause of induced earthquakes is wastewater injection associated with gas and oil extraction—not, as commonly assumed, hydraulic fracturing, or fracking. When wastewater from the extraction process is disposed of underground—typically at least 1 km deep—it increases the pressure and can cause slippage along faults. In fracking, fluid is injected for the purpose of creating cracks, but it tends to involve less fluid for shorter times, so it causes fewer and smaller earthquakes than wastewater injection, according to Justin Rubinstein, the deputy chief of the USGS induced seismicity project and one of...
