Another major earthquake on New Madrid is inevitable, geologists say it’s only a matter of time

 

May 27, 2013 – MISSOURI – It’s a bleak scenario. A massive earthquake along the New Madrid fault kills or injures 60,000 people in Tennessee. A quarter of a million people are homeless. The Memphis airport — the country’s biggest air terminal for packages — goes off-line. Major oil and gas pipelines across Tennessee rupture, causing shortages in the Northeast. In Missouri, another 15,000 people are hurt or dead. Cities and towns throughout the central U.S. lose power and water for months. Losses stack up to hundreds of billions of dollars. Fortunately, this magnitude 7.7 temblor is not real but rather a scenario imagined by the Mid-America Earthquake Center and the Institute for Crisis, Disaster and Risk Management at George Washington University. The goal of their 2008 analysis was to plan for a modern recurrence of quakes that happened along the New Madrid fault more than 200 years ago, in 1811 and 1812. No one alive has experienced a major earthquake in the Midwest, yet geologists say it’s only a matter of time. That puts a lot of uncertainty on disaster officials. Their earthquake precautions — quake-resistant building codes, for example — have never been reality tested. Some question if enough has been done to strengthen existing buildings, schools and other infrastructure. It is difficult to prepare for a geological catastrophe the public cannot see and has never experienced. “We mostly react to disasters, and it’s been extremely rare that we get ahead of things,” said Claire Rubin, a disaster response specialist in Arlington, Va. “A lot of hard problems don’t get solved. They get moved around and passed along.” Steven L. Lueker is among disaster response officials who worry about the New Madrid fault and another fault to the north, in the Wabash Valley. He’s the emergency management coordinator for Jefferson County in Southern Illinois, and he rattles off likely impact statistics. One of the most important: The New Madrid fault is expected to generate a large-scale earthquake within the next 50 years. “I may not be here when it happens,” said Lueker. “Or it may happen while we’re talking. You don’t know.” When it does happen, Lueker said Mount Vernon, the Jefferson County seat, likely will be a staging area for support flowing into Tennessee and Missouri — unless the Mount Vernon airport itself is too damaged. He doesn’t — can’t — know.  Uncertainty is the maddening aspect of earthquakes. They can’t be predicted, even very big ones. We know they happen frequently along the Earth’s tectonic plates. We also know there are no such plates in the central United States, yet that part of the country has had major earthquakes in three zones: the New Madrid fault, which on computer models looks like Harry Potter’s scar slashing across Arkansas, Missouri and Tennessee; the Wabash Valley fault in Illinois and Indiana; and the East Tennessee Seismic Zone that runs into Alabama.  These are not like the faults in California, which last had a major earthquake in 1994, when the magnitude 6.7 Northridge temblor killed 57 people and caused $20 billion in damages. The mid-continent faults rupture less often; New Madrid gets the shakes maybe 200 times a year, about a tenth the number in California. And earthquakes in the central United States tend to be smaller. The New Madrid fault appears to have a big rupture every 300 years or so; the Wabash Valley has one perhaps every 500 years.  But when quakes do hit the central United States, geology means they are felt much farther away, because the Earth’s crust in the region does not absorb the shock waves in the way it does in the Western United States. “The Northridge earthquake was barely felt in Las Vegas, 250 miles away,” said Gary Patterson, director of education and outreach at the Center for Earthquake Research and Information at the University of Memphis. “Here, a large quake would be felt 1,200 miles away in Canada.” Not everyone thinks the New Madrid fault will produce another big earthquake. Seth Stein, a geologist at Northwestern University, has argued that the small quakes occurring along the fault are not the kind that suggests the Earth is gathering energy for a large one. “He’s a smart guy,” said Patterson. “But it’s interesting that you have to go 500 miles away from the fault to find a scientist who disagrees with the consensus” that another New Madrid quake is inevitable.  At the same time, Patterson and others concede it is difficult to explain why the faults in the central United States are active at all. –DDC