Earthquakes are usually associated with the West Coast states. But they can happen in other places. The "Cape Ann" earthquake off the coast of Massachusetts damaged hundreds of buildings in colonial Boston in 1755. Memphis, Tennessee, saw a damaging earthquake in 1865, and Charleston, South Carolina, still bears the marks of an earthquake that struck the city in 1886.
Now is it Texas' turn? This month, seismic sensors near Dallas detected 11 small quakes in one day. "There have been 12 total small earthquakes in the DFW area so far this year, all centered around the old Texas Stadium site in Irving," local TV station CBS DFW reported (see: "11 North Texas Earthquakes In Around 27 Hours," by Jennifer Lindgren). "While none of the tremors have been particularly strong, they have caused a lot of concern about what to do if a big quake does strike. The most damage reported on Tuesday and Wednesday included cracks in walls and ceilings, or personal items falling from walls or shelves. But even this has residents calling their insurance agents, wanting to know if earthquake damage is covered in their policies."
Experts aren't sure what's causing the quakes, or why they're happening right now. One concern is that "fracking," the practice of injecting water and lubricants into deep rock formations to loosen up trapped gas or oil, may be a factor — either the mining operations themselves, or the associated practice of injecting waste water from the fracking process into the ground to dispose of it. That topic is a matter of debate, reported TV station NBC DFW (see: "Seismologists Disagree Over Texas Earthquake Swarm," by Noreen O'Donnell).
Reports the station: "'There are no oil and gas disposal wells in Dallas County,' Craig Pearson, the seismologist for the Texas Railroad Commission, said in a statement. 'And I see no linkage between oil and gas activity and these recent earthquakes in Irving.' But a geophysicist from the U.S. Geological Survey said an investigation must look at all possibilities. 'It's too early for us to say that we don't see any connections yet,' said Robert Williams, a coordinator with the U.S. Geological Survey Earthquake Hazards Program in Golden, Colorado. 'We don't want to rule anything out at this point.'"
And Federal authorities say the recent activity may indicate an increased risk for the area, the Dallas Morning News reported (see: "USGS likely to upgrade North Texas' quake risk level," by Anna Kuchment). As fracking practices become widespread, government experts say they're seeing an increase in small tremors associated with the oil and gas extraction activity.
"This year, for the first time, the USGS will include quakes believed to have been caused by human activity in its National Seismic Hazard Map, which engineers use to write and revise building codes, and which insurers use to set rates," the paper reports. "Between 2010 and 2013, people living in the central and eastern U.S. felt five times as many quakes per year, on average, as they did between 1970 and 2000. Scientists have linked many of these earthquakes to human activities, including parts of the oil and gas production process. While larger quakes are unlikely in North Texas, scientists can't rule out the possibility. In 2011, a 5.7-magnitude temblor struck near injection wells in Oklahoma, causing widespread damage."
"An injection well can reach more than 10,000 feet deep, pumping tens of millions of gallons of untreated water a year into underground rock formations and sometimes the very faults that cause earthquakes," explained the Dallas Morning News in a January 10 story (see: "What's at fault? Scientists seek cause of Irving earthquakes," by Anna Kuchment, Randy Lee Lofti, James Osborne, and Avi Selk).
But linking fracking processes to seismic events is an imprecise enterprise. Earthquake expert Cliff Frohlich, a University of Texas at Austin seismologist, told the Morning News, "It's like cancer. You can never really prove someone got lung cancer because they smoked. All you can do is look at the statistics and say you're more likely to get cancer if you smoke."
"In 1902, there was a big earthquake in Austin," Frolich said. "You know that wasn't fracking. But if it happened at D/FW airport tomorrow, you'd wonder if it was."