With Great Uncertainty, Geologists try to Predict the Chance of a Big Quake Striking Kansas
Between 2003 and 2012, there were three earthquakes in Kansas, but since then, there have been 579.
(TNS) - Lori Lawrence said she was standing in the hallway of her home near Central and Hillside on Wednesday night when the bedroom door started rattling. It was, she said, the sixth earthquake she’s felt in the past two years.
Friends filled up her Facebook feed with comments about the latest quake, which was actually two back-to-back quakes, the largest of which had a magnitude of 4.8.
It was intense enough that the city of Wichita, for the first time, sent out a team to examine whether any of its infrastructure had been affected by an earthquake. Reports had already been coming in about three water lines that had burst around the time of the quake. After a day of inspections, a few more potential cracks had turned up, including one at a wastewater treatment plant.
In the past two years, Lawrence has become one of the leading organizers for the Kansas chapter of the Sierra Club trying to document local damage from earthquakes. In November, the legal nonprofit Public Justice posted on behalf of the Sierra Club a notice of its intent to sue four of the largest fracking companies in Kansas and Oklahoma to prevent them from continuing to inject wastewater that many scientists say is probably causing the earthquakes.
But even as Lawrence and others are trying to document possible damage from low-level shaking, scientists are estimating the likelihood of a much larger earthquake in the area.
Between 2003 and 2012, there were three earthquakes in Kansas, but since then, there have been 579. This number doesn’t include more than 900 quakes in Oklahoma in 2015 alone, nor the 70 quakes in the first week of 2016. Oklahoma’s earthquakes have been creeping farther north, until in 2013 they reached the Kansas state line. In 2014, Kansas experienced the largest earthquake recorded originating within the state. But the two most intensely felt recent earthquakes in Wichita, in November 2015 and on Wednesday, originated in Oklahoma.
Because of the increase in the number and severity of earthquakes, the U.S. Geological Survey has had to change how it maps earthquake risks and devise new ways of measuring risk locally.
The new measurements suggest a potential for an earthquake much more severe than what most structures in southern Kansas have been built to withstand.
But the new predictive models may not be anywhere near as accurate as the ones along traditional seismic plates, according to Todd Halihan, a professor of geology at Oklahoma State University.
“The predictions kind of suck,” Halihan said. “We’re somewhere between a couple of liquor bottles falling off the shelf and complete Armageddon. And that’s not particularly comforting or useful, so you should probably take some steps to prepare people for what to do that is logical in a case of uncertainty.”
The USGS makes what are called “hazard maps” that reflect how likely an area of the country is to experience a large earthquake that could cause catastrophic damage. These maps draw on hundreds and thousands of years of historical and geological data about when earthquakes have occurred in the past and where known fault lines are.
But when the USGS scientists were making the map for 2014, they realized that the thousands of small earthquakes in Kansas and Oklahoma that were likely caused by humans were throwing off their models. If they left in all the recent local earthquakes, south-central Kansas and Oklahoma would suddenly look like a relatively huge risk for a major earthquake.
That’s because in a typical active fault zone, such as those found in California, the number of earthquakes that have become a regular event here would be an indicator of a potentially large future earthquake.
But USGS studies have indicated that these local earthquakes probably follow a different pattern. Their likelihood increases the more wastewater is injected underground in some areas, and the earthquakes subside when the wastewater disruptions are lowered or halted.
But that wasn’t a satisfying answer for people who wanted to know the short-term likelihood and danger of earthquakes in Oklahoma and Kansas. So in April, the USGS began creating separate, short-term hazard maps that estimated the chance of experiencing a catastrophic quake here. These maps put the recent upsurge of local earthquakes back into their model.
And, instead of appearing light gray or dark gray, which implies a low level of earthquake risk, south-central Kansas and a huge area of central and northern Oklahoma now appear red and orange.
There are only three places in the lower 48 states that appear red on the USGS’ 2014 50-year hazard map. One is the San Andreas Fault in California, which includes San Francisco, the site of the 1906 earthquake, the largest in U.S. history outside of Alaska. The 1906 quake killed around 3,000 people and destroyed most of the city. Another is the New Madrid Fault in far southeast Missouri, the site of the second-largest quake in U.S. history. That quake, which occurred in 1811, was described by witnesses as a “distant thunder” that caused trees to crack and fall, rivers to overflow their banks and the sky to turn black.
The red areas of the maps are the places in which there is a 2 percent chance of one the most severe earthquakes occurring in the next 50 years. These are the devastating kinds of quakes that do strange things, like make the Mississippi River flow backward, as happened in 1811, according to Halihan.
These earthquakes are relatively rare.
Instead of modeling over 50 years, the new USGS maps for Kansas and Oklahoma cover just one year. They show a 1 percent or less risk of a major earthquake occurring during the year.
If this rare event happens, even the most-up-to-date buildings would experience earthquake forces as much as or more than 20 times greater than what they were built to withstand based on current building codes.
Only the most southern Kansas counties, such as Harper, are colored red. But Sedgwick County and Wichita are close enough that they would still experience forces a number of times greater than what building codes dictate new buildings should withstand.
After Wednesday’s earthquake, Richard Meier, the chief building inspector for the city of Wichita, told his boss that they should start looking into whether the city should change its building code to reflect the threat posed by the recent earthquakes.
Normally, the process of changing building codes is slow at the international level and at the city level, according to Meier and several local architects.
The codes “are not going to change a great deal, and the reason for that is because the seismic activity that we’re experiencing in south-central Kansas and Oklahoma, in geological periods, is a very recent phenomenon,” Meier said. “So when the geophysicists and geologists look at this data, they simply don’t have enough background to make accurate predictions for a long period of time like they have been doing on the tables on the past.”
In fact, Meier’s current big push is to upgrade the city’s building code from the 2006 version of the International Code Council to the 2012 version.
The code would cover earthquake protection only for new or remodeled buildings, according to Meier. He said he has received only one call about potential building damage due to an earthquake, and that wasn’t correct. But he said he receives a couple of calls each quarter from local builders and architects asking whether they should be doing anything in light of the increased quake activity.
“More and more people are asking questions and wanting to know,” Meier said. “We do have the building community that is kind of waking up and saying, ‘Hey, wait a minute, do we need to start doing something here?’ ”
Until Thursday, Meier didn’t know that the USGS had already released new short-term predictive maps. Even after seeing the maps, he said it would be a long process before anything would be adopted.
More stringent building codes would come at a cost, he said.
“That certainly affects prices of buildings and what ultimately owners are going to have to pay to get a structure built, so it’s an economic thing as well as a safety thing,” Meier said.
But by the end of the day Thursday, Meier had told his boss that, after he finished implementing the 2012 codes, he would gather together experts to make a determination about whether the local building codes would need to change.
Some people think that Kansas buildings are already strong enough to withstand a large earthquake because they have to be built to withstand strong winds.
But buildings require a different kind of reinforcement in order to withstand shaking back and forth as opposed to withstanding forces from wind, which tends to come from a single direction. In an earthquake, the top of a building can be pushed one way while the bottom is pushed another, causing even buildings that can withstand strong winds to separate from their foundations and collapse.
How real is the threat?
Many geologists have been operating on the assumption that the largest magnitude earthquake Kansas or Oklahoma might experience would be around a 5.6. That was the magnitude of the largest recent quake in Prague, Okla., in 2011, which caused around $10 million in damage and sent several people to the hospital.
But scientists at the USGS have been unwilling to rule out the possibility of a magnitude-7 quake.
One reason is that the latest earthquakes have been activating old fault lines, some of which they didn’t know existed, according to George Choy, a research geophysicist at the USGS in Colorado.
Sedgwick County’s own hazard analysis plan from 2011 points out that a 300 million-year-old underground mountain range, the Nemaha Ridge, runs right through Sedgwick County, from approximately Oklahoma City to Omaha. Nemaha is thought to have been the source of the largest recorded earthquake in Kansas just outside Manhattan in 1867.
And no matter the strength of the earthquake, there is reason to believe the local area is particularly vulnerable.
One reason is that earthquakes in the Midwest can be felt farther away than many coastal earthquakes, according to Halihan, the professor at Oklahoma State.
The soil in the Midwest tends to be stiffer than that on the coasts, according to Halihan. It’s like dropping a rock on concrete versus in mud – the sound waves are going to travel much further when it hits the concrete.
And most of the quakes in Kansas and Oklahoma are relatively shallow, he said, meaning they don’t have to travel as far to reach the surface and their force won’t dissipate as much.
“Usually the folks from Seattle go, ‘What are you guys complaining about? It’s just a 4.7,’ ” Halihan said. “4.7’s here are a hell of a ride.”
In addition, the type of soil in Sedgwick County only accentuates the shaking, according to Rex Buchanan, director of the Kansas Geological Survey.
Much of the county sits in a basin of stone, silt and clay. Clay soil, like that found in much of eastern Wichita, is particularly susceptible to shaking. So when an earthquake’s force reaches the city, it feels a bit like a bowl of jelly that’s been shaken, Choy, the USGS scientist, said.
Once the shaking starts, not all buildings will be affected equally. Taller builders, older ones and buildings held up by brick or masonry will, on average, tend to see worse damage, whereas wooden and steel buildings may be more resilient.
The USGS is planning to release new short-term hazard maps in March, which may or may not imply such catastrophic possibilities for Oklahoma and Kansas.
The current map “was their first attempt,” according to Halihan.
The USGS’ first predictions were largely statistical, he said, but if their scientists really believe that a catastrophic quake is possible, that implies the existence of a long fault line. The larger the fault line that moves, the larger the earthquake. But even the Nemaha Ridge, he said, isn’t oriented in a direction that would be likely to shift.
“You need a really long chunk to move to make that big of an earthquake,” Halihan said.
Because the consequences of a large quake occurring are so severe, he said, it makes sense to at least take low-cost precautions, such as having kids learn to duck under their desks at school. One of the main ways people get injured in earthquakes is that, instead of ducking for protection, he said, they run outside and get hit by a falling piece of masonry. “It’s not that you couldn’t survive where you’re at,” Halihan said. “It’s that you tried to get to someplace safer, and that was a bad call.”
Although Wichita public schools instituted an earthquake plan in 2014, it is optional for principals to implement earthquake drills in their schools. According to a district spokesperson, it is unclear whether any principals have yet started such drills. Earthquake drills are required in cities like San Francisco, which have been colored red or orange on the hazard maps for much longer.
In 2015, the Kansas Corporation Commission limited the amount of wastewater that oil companies are allowed to dispose of deep into the earth in Harper and Sumner counties. More than a half year after these changes came into full effect, the commission reported that there is some evidence the number and severity of earthquakes originating in Kansas may have fallen in the second half of 2015.
The fall in the price of oil the past two years, now trading at less than $35 a barrel, could continue to mitigate the chances for more Kansas quakes. Many of the new wells that companies tried drilling farther northwest into Kansas were not that productive even before the price of oil dropped, according to Buchanan, director of the Kansas Geological Survey.
“A lot of the wells didn’t work and produce enough oil for the amount of water they were producing,” Buchanan said. “Water is heavy and it’s expensive to bring it to the surface, especially if you have to inject it back to the deep subsurface.”
But the Sierra Club has filed an intent-to-sue letter, hoping to require a more ambitious reduction in the disposal of wastewater from fracking, which would include Oklahoma. According to Richard Webster, an attorney with Public Justice, which is filing the lawsuit on behalf of the Sierra Club, it does not have to prove that an earthquake has caused harm, just that there is a reasonable risk it may. They want to create an independent body that will be able to make recommendations of what a sustainable level of injecting wastewater is.
“One of the problems is that everyone is chasing this problem. Instead of getting ahead of the problem, everyone is waiting,” Webster said. “There is an earthquake and then the fluid injection in that area is reduced slightly, and then it occurs somewhere else. You can’t just chase the problem around the states.”
One city that has been taking a more proactive approach is Irving, Texas, which has been working with the USGS to model different scenarios for what might happen if earthquakes of various magnitudes hit the area, according to Choy.
Get quake insurance
Although earthquakes have become a more serious concern in Sedgwick County, according to Dan Pugh, the emergency response manager, the concern is still not very high.
“It wasn’t super-high beforehand, and it’s still not super-high,” Pugh said.
Pugh said county emergency response workers check in with cities to see whether there is damage after earthquakes.
But he said one of the main messages he has been spreading is for homeowners to buy earthquake insurance.
Buchanan of the Kansas Geological Survey said that while he doesn’t know anyone who would rule out a magnitude-7 quake, he hasn’t heard anyone talking of a quake with a magnitude larger than 6, in part because the largest one recorded since the recent earthquakes started in Oklahoma so far has been a 5.6.
But he said there also are questions about the impact of smaller quakes.
Buchanan said he has been talking with the state transportation department about the potential effects of the kind of “repeated, low-level shaking” the state has already seen.
It’s not clear what repeated low-level shaking might do to water lines, roads and buildings, he said, adding: “That question is really in its infancy.”
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