It’s a real risk in Dallas now.
The Dallas-Fort Worth area has a 1 to 5 percent chance of experiencing an earthquake strong enough to damage buildings in the next year, the U.S. Geological Survey said Monday.
That risk has grown tenfold since 2008, when the area began experiencing a surge of mild to moderate-sized quakes, said Mark Petersen, chief of the National Seismic Hazard Mapping Project at the USGS in an exclusive interview with The Dallas Morning News. North Texas’ earthquake hazard is now on par with parts of Oklahoma and California.
“One of the big concerns for me is that there is a very high population density in the Dallas-Fort Worth area, and this activity is taking place within that area,” he said.
Last week, The News obtained a report, produced by the Federal Emergency Management Agency, detailing the potential damage from earthquakes of magnitude 4.8 and 5.6, which fall within the hazard map predictions.
The vast majority of damage to buildings would be minor, such as cracks in walls and ceilings. “I don’t want people to feel like their houses are all going to come down,” Petersen said.
But he said he couldn’t rule out a larger earthquake because the Dallas-Fort Worth area has long faults running through it that may have the potential to rupture.
A decade ago, an Oklahoman could count the number of noticeable quakes on her fingers. “In this past year, we had over 900,” says USGS seismic hazard expert Mark Petersen. “So the rates have surged.”
Petersen says induced quakes have become more frequent because there’s more wastewater from oil and gas operations around the country that has to be disposed of. Companies pump it down into underground wells, and sometimes that water raises pressure on underground faults that then slip and cause small quakes.
Industry officials say the percentage of waste wells that pose quake risks is very low. But with the rise in hydraulic fracturing (fracking), which produces a lot of polluted water that needs to be disposed of, the overall number of waste wells around the country has skyrocketed.
The new maps also include the risks of natural quakes around the country, as they have in the past. Those risks haven’t changed much. But the number of induced quakes has increased tenfold since 2014, according to the USGS.
Petersen notes that most of these induced quakes are not likely to bring down buildings. Most are in the range of magnitude 3 or 4, which are minor. But some are above magnitude 5, which can do serious damage — cause cracks in your house, for example, or in bridges and roads.
“I think that we need help people understand that they do face a risk in these areas of induced earthquake activity,” Petersen says, “and they need to take precautions just like people in California do.”
Taking precautions against induced earthquakes — such as strengthening buildings or changing insurance rates — might be tricky, though.
Mark Zoback, a geophysicist at Stanford University who studies induced quakes, says: “It’s important to recognize the risk that these maps point out, but that risk is going to change depending on what’s happening on the ground.” Wastewater wells may not be active for more than a few months or a year; after that, they may no longer pose a risk. Meanwhile, it can take years for a state or community to change building codes to make structures more quake-sturdy.
Moreover, some states have started to ban or limit waste wells in these quake zones. “And in the few places where the injection has stopped,” Zoback says, “the earthquakes have stopped.”
Zoback adds that the boom in oil and gas exploration in some places is dwindling, which would likely mean fewer waste wells and lower risk. On the other hand, wherever the industry drills new waste wells could become the next quake hot spot.