Uptick in New Madrid seismic zone activity within normal ranges
Data from the U.S Geological Survey shows dozens of earthquakes in the New Madrid seismic zone, which includes far western Kentucky and Tennessee, within the past 30 days.
The zone isthe most active area in the U.S east of the Rocky Mountains.
Gary Patterson, a geologist with the Center for Earthquake Research and Information in Memphis, said the recent uptick in activity isn’t unprecedented for the fault.
“We have 350 earthquakes per year that we can accurately locate, and there's probably twice as many that are happening that are very small that we can't locate, so they don't go into catalog,” Patterson said, “In the last two weeks, we've had several earthquakes, but I wouldn't count any of them outside normal activity…If we had three magnitude fours and a magnitude five in a month, then we would say that's out of the normal, and we should be watching it very, very closely.”
Patterson also called the frequency of earthquakes in the area a “scientific enigma.”
Most earthquakes occur on plate boundaries —places like California — not in the middle of a tectonic plate, like the New Madrid Seismic Zone. According to Patterson, the energy which drives plate boundaries is predictable and dependable, but the energy in the central United States is somewhat of a mystery.
“If we continue to monitor earthquakes over time, we could kind of have a better picture of the fault system, and we can see where [the system] is and where it intersects with lifelines. As far as how much you can store that energy or energy that is transferred during an earthquake from one to the other —those are the things that we don't understand,” he said. “I think the main thing is that the size and the number of earthquakes that have occurred here over history, there's nothing like it outside of a plate boundary.”
The population densityand energy disbursementare considerable factors when it comes to earthquake research. In the western United States, there are lots of faults and space for energy to fizzle out. However, in the central part of the country, there is a cold, hard slab which allows energy to travel greater distances. In other words, Patterson said a large “one state” earthquake in California easily becomes a five state event in the central United States.
Patterson said further investigation in the region would be costly and would better benefit places like California, where hazards are more frequent and seemingly catastrophic.
“Even though more states are involved [in the New Madrid Seismic Zone], the infrastructure out west and the population is much larger, so their risk is going to be very, very high. It's what you stand to lose —what's the exposure—not just casualties. Although these earthquakes here are felt over a larger area, we have less stuff, less expensive stuff than along the coast,” he said.
“The hazard is there,” Patterson warned, “but it just doesn’t relate to the human timespan. These are measured in geologic time —hundreds of years— but the clock is ticking.”
Although most research relies on past earthquakes, geologists like Patterson remind communities that future preparation is paramount. Some of the ways he said areas can prepare is by evaluating state building code and emergency response.
For example, some buildings in downtown areas, once made for cotton mills and button factories, have now been turned into apartments. However, Patterson said these buildings are rarely brought up to code to survive major earthquakes.
“Lack of a standardized building process can really upset the apple-cart when you're responding to a disaster. And those will actually be things that we could have prevented, that will drag us down in responding to a disaster,.” he said.
Danny Jowers, the director of emergency management in Obion County, Tennessee, said that standardized codes would better protect people from the common earthquake. He stressed the importance of simply having a plan.
“[The response] is all going to depend on how large this earthquake is and how widespread the damage is. That's the bottom line. Is it going to be magnitude seven or is it going to be magnitude nine?” Jowers said.
“Our biggest challenge is mitigation, which is trying to help if something happens beforehand, meaning getting everything ready. We're trying to mitigate things that would cause it to be less severe.”