Damage would 'blow people's minds': How a major earthquake could devastate Evansville

Earthquakes have occasionally rocked our region since North America almost snapped apart hundreds of millions of years ago. The Earth continues to shift along the resulting fractures beneath its surface, releasing energy that ignites quakes. At their smallest, you can’t even feel them. They shake the area no more than rush-hour traffic screeching down the Lloyd Expressway.

But if “the big one” hits, it would be unlike anything we’ve experienced before.

The Courier & Press interviewed multiple geologists for this story, as well as some of the local, county and state officials who would leap into action if such a disaster occurred. None of them could say for sure what would happen. No one in the world knows that. But they all painted grim pictures of the potential aftermath.

An earthquake as big as 6.8 would endanger hundreds of lives and seriously damage thousands of buildings — most notably homes and several older, brick schools. In some parts of the city and region, the quake could snap water mains and force officials to shut off natural gas service to avoid leaks and fires. The resulting damage would overwhelm first responders and make it difficult for them to traverse the roads, potentially leaving some residents to fend for themselves for days or weeks.

Because of the Ohio River and an assortment of creeks, you can’t move through the area without crossing countless bridges. Some would fail. Others, such as the Twin Bridges, would likely hold up, but there’s a possibility some of their approaches could crumble.

Some of the resulting damage — water and dirt erupting from the ground; the possibility of coffins rising in the newly liquid soil — may not even seem real when it’s happening.

“It would blow people’s minds,” May said. “They can’t visualize it, so they don’t think it occurs.”

The Wabash and the New Madrid

Most Midwesterners have probably heard of the New Madrid Seismic Zone. It walloped the region in 1811 and 1812, creating a series of quakes so wild and strong that they temporarily reversed the flow of the Mississippi River.

New Madrid inspired everything from Native American legends to country-rock songs, and it came howling back into our lives when a failed doomsday prophet named Iben Browning said there was a 50-50 chance of a gargantuan quake hitting the region on or around Dec. 3, 1990. His prediction, which thankfully fizzled, triggered a media bonanza and sparked mass panic in residents from Missouri to Illinois to Kentucky to Indiana.

But according to recent studies, the greatest threat to Evansville wouldn’t come from New Madrid, but from a much closer, less famous cousin that hugs the border between Southern Indiana and Illinois: the Wabash Valley Seismic Zone.

“A lot of the attention has been on the New Madrid Fault, but the Wabash Valley Fault could be the more dangerous one,” Douglas Wiens and Michael Wysession, seismologists at Washington University in St. Louis, wrote in the days after the 2008 quake, which originated in the Wabash. “There hasn’t been a magnitude-6 earthquake on the New Madrid zone in more than 100 years, yet in 20 years there have been three magnitude-5-or-better earthquakes on the Wabash Valley Fault."

A 6.8 on the Wabash would be 251 times stronger than the one in 2008 and about the same magnitude as the Loma Prieta disaster in 1989, which killed 63 people, injured almost 4,000 and saddled the San Francisco area with billions of dollars in damage.

A quake that size could be just as bad here. This is the interior of the United States – a place with much less stringent building codes than California and a populace that treats earthquakes as a faraway fear.

Indiana and Kentucky have taken some precautions to steel themselves against disasters. Buildings constructed within the last 20 years, such as the Ford Center, are often built deep into the bedrock and would likely weather a large quake. And Vanderburgh County keeps an updated “multi-hazard mitigation plan” on file in the event of a calamity.

Past local and state officials, however, have fought against strengthening residential building codes. The state code committee loosened them just last year, Evansville Building Commissioner Dave Ballew said.

“Cost is the biggest thing. You weigh the pros and the cons. Are we going to add $3,000-$4,000 to a house to make it more stringent or is the possibility of something" remote, he said. “We are going to have an earthquake at some point in time. But I don’t know when that is. No one knows when that is, really. Is it worth adding the extra (cost) onto a home, or is it going to keep development stifled in this area if we do that?”

Any updates wouldn’t protect buildings built under the old codes anyway. And retrofitting structures can be horribly expensive.

It all gets at a difficult question: How do you prepare for something that could either happen tomorrow or not in your lifetime?

“We don’t how bad it’s going to be until after it happens,” said Cliff Weaver, the director of the Evansville-Vanderburgh County Emergency Management Agency. “Then we can figure out what we need to fix.”

Weaver and Ballew stressed the importance of disaster preparedness classes — some of which are held at neighborhood association meetings. They don’t want to scare people. They just want them to be ready.

“Think about what you’d do if you couldn’t get access to money because the ATMs are down. You have no place to stop for bread or whatever because you can’t get to the stores,” Ballew said. “Most of the time you take for granted the little things. Try to live without (them) for a 48-hour period and see what happens.

“No Internet, no TV, no phone. What would you do? Could you survive?”

Liquefaction + acceleration: a ‘double whammy’

The amount of damage you could suffer all depends where you live — and what kind of ground rests under your feet.

A few years ago, the USGS teamed with Purdue University, the University of Memphis and several others to complete what they called the “Evansville Area Earthquake Hazards Mapping Project.”

You can find it online. Using a 6.8 Wabash earthquake as a model — what May called the “bomb blowing up” scenario — they attempted to show what portions of our area would be hit the hardest.

The monstrosity of a quake is determined by several factors. But two of the most important are peak ground acceleration (PGA) and liquefaction potential (LPI) — or the likelihood that certain types of sediment would liquefy under the stress of shaking.

Liquefaction is more probable in areas with sandy, porous soil that take on water fast. That includes Downtown Evansville. Rocky or hard soil is less susceptible.

There are several spots in the city where high liquefaction and strong acceleration would overlap, causing what May called a “double whammy.”

The largest of those nestles along a sand-riddled stretch in the horseshoe of the Ohio River, not far from Ohio Street and the Port of Evansville. To see liquefaction at the surface, all you need is about an LPI value of 5, May said. In that part of the city, it could reach as high as 12 or 15.

Meanwhile, the ground would “shake like hell.”

“You would see fissures in the ground,” May said. “They call them sand volcanoes. You would see sand coming to the surface … and piling up.”

Liquefaction lies behind those horrifying videos you can find online of the magnitude-6.9 earthquake that drubbed Indonesia in 2018. Whole houses slid across the land as if they were on conveyer belts.

That likely wouldn’t happen to the tall, newer buildings along the river, such as the Old National or CenterPoint headquarters. They were built to strict standards. But slab houses and older high-rise buildings set in porous soil may not be so lucky.

Occasional earthquakes in the Midwest are not new. But geologists say a 'big one' could strike the region unlike anything we’ve experienced before.

The strongest ground acceleration in Indiana would likely occur in areas closest to the probable epicenter in Illinois: Gibson, Posey, and the western slabs of Vanderburgh, near Reitz Hill and the University of Southern Indiana. But the intensity of the shaking could vary wildly across the region.

The reason for that, May said, is surface geology.

The Evansville area is riddled with different types of topography. In a 15-minute drive, you can move from low-lying river bottoms to rocky hills. And in 2008, May said researchers stumbled across something strange.

After the quake, some residents went to a USGS website called “The Shake Map.” There, they could report where they lived and the intensity of any shaking they felt. Researchers soon realized that people who lived along surface geology borders — where the land changes from lake beds to uplands, for example — reported feeling more intense shaking than others.

Some surface geology would also allow surface waves to become more “bouncy,” May said, which could determine what kind of damage — and danger — would occur.

On Nov. 9, 1968, a 5.3-magnitude quake rumbled through the Evansville area on a cold Saturday morning. Chimneys toppled and windows shattered. Vibrations reverberated through at least 24 states.

May was only a boy then, growing up in Posey County. It was the first earthquake he ever experienced in person. He could see items vibrating on top of the refrigerator. Wheelbarrows jostling across the yard.

Looking back, he realizes he was seeing something called "ground roll."

“That’s the stuff that kills people and does damage,” he said.

How bad will 'the big one' be?

Until the day the big one hits, we can’t say that much for certain. There are too many variables.

If it’s spring and the ground is saturated with rain, liquefaction could be a bigger problem. If it hits in the middle of the day – when people are crowded into schools and office buildings or swarming through the streets for lunch hours and commutes – the number of injuries and deaths could rise higher than if the seismic activity flared up in the middle of the night.

But several simulations run by USGS, the Central United States Earthquake Consortium, the Polis Center at IUPUI and others try their best to paint a picture of what could occur in our area.

Here’s what could happen to the Evansville area if a magnitude-6.8 earthquake erupted near Mount Carmel, Illinois, in the Wabash Valley Seismic Zone, based on those and other research materials, as well as interviews with geologists and local officials.

? More about Evansville earthquakes: Everything to know about fault lines in Indiana and the possibility of 'the big one'

The ‘bomb’ goes off

The strong shaking would only last a few seconds — anywhere from 15 to 30. But the feeling could linger much longer.

Anything not bolted down would be the first to fall — appliances, bookcases, items on shelves. Windows would shatter. Ceiling tiles would plummet in piles. Chimneys and any unreinforced brick would falter, as well, sending debris toppling to the ground.

All this could lead to injury and death. It's tough to pin down an accurate estimation of fatalities. The numbers are all over the place across different studies. But injuries could stretch into the thousands — many of them serious.

People would be separated from their families. And if cell phone towers go down, they would have limited ways to contact them.

Area hospitals and medical facilities could be hit as well, potentially hampering their ability to care for a large influx of patients.

“Mass relocation may be necessary, but the residents who are suffering from the earthquake can neither leave the heavily impacted areas nor receive aid, or even communication, in the immediate aftermath of a significant event,” a 2014 Polis Center report reads.

Thousands of buildings would suffer serious damage. In Vanderburgh County alone, more than 9,000 structures — about 14 percent of our entire stock — would at least be hit with moderate damage, with more than 400 damaged beyond repair, according to the Polis Center. The vast majority of those would be single-family homes.

The damage would be much worse in counties closer to the epicenter. In Southern Indiana, Gibson would get the worst of it. About 60 percent of their total buildings would take at least a moderate hit. More than 2,000 couldn't be repaired — about half of which are homes.

Posey County would also see serious damage, as would Warrick, Knox and others.

Since Henderson, Kentucky, is farther from the epicenter, the damage could be less severe, but still serious.

“I do know that most of the historical downtown buildings would not fare well in the event of a major earthquake due to types of construction and our types of soil in the area,” said Randy Tasa, Henderson County’s codes administrator. “Structures and homes situated along the riverbank would likely see the most damage. I do believe that the single-story homes located away from the river would fare much better, but could still have significant damage depending on the magnitude of the earthquake.”

Commercial buildings built within the last 20 years should hold up, he said.

Some Evansville schools, however, wouldn’t do as well. Evansville Vanderburgh School Corp. spokesman Jason Woebkenberg said the school system “follows statutory guidelines for conducting monthly emergency preparedness drills.” But damage to some of their buildings may be unavoidable.

According to Vanderburgh’s hazard mitigation plan — which uses a 7.1 as its model, not a 6.8 — more than half of Evansville’s schools could suffer some kind of damage. More than 20 would be lost causes.

And if the earthquake struck while school was in session, it could also injure several students, teachers and staff members.

“They’re older buildings,” Ballew said about some of the schools. “A lot of times they’re (retrofitted). But to retrofit an older school almost cost more than what it would cost to build a new school.”

Then there are Vanderburgh County’s 20 dams and 73 hazardous material sites identified in the Polis report. They could hurl even more wrenches into the aftermath.

While the structural damage occurred, the Earth would be changing around us.

Large waves could churn in the Ohio River and slosh onto shore. Riverbanks could cave in. Boats could capsize. Along fault blocks, some areas would sink while others would rise.

Liquefaction would kick in quickly. In sandy or pea-gravelly soil, the land and water would separate, the resulting pressure sending water and sediment “squirting out of the ground like a volcano,” May said. If the acceleration and liquefaction were strong enough in tandem, in-ground swimming pools, and even basements on homes without structural integrity, could “pop up” like boats. Coffins could, too, said Paul Doss, a geology professor at the University of Southern Indiana.

Foundations could crack. Slab houses subject to liquefaction could slide or even sink a little.

“It’s not like one of these dramatic things where (houses are) gonna disappear in quicksand like in the old movies,” May said. “It isn’t like there’s going to be a big crack opening in the road and we’re all gonna fall down in it. This stuff is more like, there’s going to be a lot of older buildings which were not designed for a modern earthquake. … And people are not going to be pleased. Because they’re going to have to raze a lot of buildings.”

Bridge and road damage could leave residents stranded

Earthquakes in California leave giant cracks across the roads. Things wouldn’t play out that way here.

“(Our) faults are deep down in the subsurface,” Doss said. “We wouldn’t see a surface expression of them.”

There would still be plenty of damage. Power lines could come whipping down and trees could keel over, covering roadways with dangerous debris. Driving would become perilous at best and impossible at worst.

Slews of creeks cut through Evansville, leaving our ability to cross town at the mercy of several old city and county bridges. Everything pre-1970s was constructed with basically zero seismic standards in mind, county engineer John Stoll said. Those could fall apart under the stress, especially if they’re built on stone abutments, such as the Stringtown Road bridge over Pigeon Creek.

Damage to multiple bridges would essentially divide the city in two, Weaver said.

The Twin Bridges and passages along the Lloyd Expressway are a different story. The Indiana Department of Transportation maintains those, and spokesman Jason Tiller said most structures along the interstates and the Lloyd are either retrofitted or built in the last 20 years, after seismic designs took a major leap.

“Anytime there’s been a bridge project, any kind of reconstruction or resurface — within those rehabilitation contracts it’s mandated that (workers) bring them up to the current standard for seismic resistance,” he said. “We’ve had a lot of bridge projects in the last five or six years that have done that.”

The approaches to the bridges, though, may be a problem. Some could crumble, leaving motorists stranded.

Tiller and the engineers with INDOT believe the approaches would hold up — “we’ve prepared and prepared and run models” — but because the area has never seen an earthquake of this size before, Tiller can’t say for sure.

“A 6.8 or 7, it could be different,” he said.

Water and gas may be vulnerable

On April 18, 1906, a pair of disasters hammered San Francisco.

A massive earthquake exploded along the San Andreas fault just after 5 a.m. It did plenty of damage on its own, but the worst destruction came from something else: ruptured gas and water lines.

The leaking gas ignited fires all around the city. And without access to water, firefighters were essentially disarmed.

“Odds are, if we have that type of earthquake, the natural gas grid will be shut down no matter what — just to save the gas and prevent leaks and fires,” Weaver said. “If the water mains are ruptured and broke, too, that just makes things more complicated.”

CenterPoint keeps plans on file to respond to any kind of natural disaster, but spokeswoman Alyssia Oshodi said she couldn’t share them publicly.

“In the event of a natural disaster … we would work in partnership with local city and county officials to monitor the event and coordinate actions, while keeping our customers’ safety top of mind,” she said.

The Evansville Water & Sewer Utility was more forthcoming.

Workers have replaced more than 50 miles of antiquated water mains in recent years, and the project is still ongoing, officials said in written responses to the Courier & Press. The work has focused on the skinny cast-iron pipes that have lurked under the city for more than 80 years.

But some of those pipes are still down there, and they would cause the biggest problems in the event of an earthquake. Parts of town that depend on them could be without water the longest — the same areas often dogged by water-main breaks and boil advisories. Isolated flooding could arise. Officials would also strive to protect any water left in our tanks and reservoirs.

Then there’s the possibility of contamination. Chemicals and microorganisms can wiggle into busted pipes and leave water unsafe to drink. The utility said it would test water quality as soon as all the repairs were made. But that could take some time.

The aftermath — and how to take care of yourself

After it all ended, we’d start hearing helicopters.

FEMA maintains 28 urban search-and-rescue teams around the country, Weaver said. The closest is based in Indianapolis, and once a disaster declaration came down from the federal government, they’d chopper to the city to establish a base camp.

Weaver would coordinate the local response. Ballew and people in the building commissioner’s office would survey the damage, paying close attention to essential buildings and anything with a “potential fall hazard,” such as chimneys.

Stoll’s team, meanwhile, would do “two things right off the bat”: take a close look at every bridge that crosses Pigeon Creek, and make some calls to Indianapolis.

The engineer’s office doesn’t have any INDOT-certified bridge instructors on staff, so in the aftermath they’d depend on Indy workers to aid in the effort.

Police and firefighters would be inundated, as well. Damage and humanitarian needs could keep them busy for days.

That’s why it’s imperative for residents to have a plan.

“There are things one can do — and they’re gonna work whether it’s an earthquake, a zombie apocalypse or an ice storm,” Doss said. “Know where you can get some food. Know where you can get some water. Know where you can get a Band-Aid. Generally, people should be ready to be OK for a few days. Or a week. Or a month.”

Ready.gov offers simple but key suggestions.

Pick a place to meet up with family members in the event of a disaster. Keep a “go bag” in a safe place in the house (never the basement) and stuff it with essentials such as canned food and a first aid kit.

? What you can do: Here are 4 ways to prepare for the major earthquake that could hit Evansville one day

Water will be imperative as well, especially if there's a disruption in service.

Indiana residential building codes no longer require you to strap down your water heaters in seismic-prone parts of the state, but you should anyway. Remember: there are at least 40 gallons of potable water in there, Ballew said.

Back in 2000, the International Code Council tried to tighten the seismic requirements for new Southwestern Indiana homes in a big way — way beyond wrapping a strap around your water heater. The changes were so sweeping, local officials feared at the time, that they would essentially ban basements and increase construction costs by as much as $19,000 on large homes.

So a task force comprised of builders and Vanderburgh County officials rushed to scale back requirements. They said their changes protected homes without adding unnecessary costs. Similar backlashes have occurred over the decades, and today area counties are well below the highest seismic standards.

But there’s no law against going beyond the code – if you can afford it. If he were building a new house, Ballew said he would do things such as add rebar in the concrete or install ports so he could tie down anything that needed it.

People in older homes, and with less money, may not have those options. They would be the ones most at risk in an event like this. But they could spring for earthquake insurance to give them some peace of mind.

The prediction: Was it credible?

“All my daydreams are disasters.” — Uncle Tupelo

The question has loomed over the Midwest for decades. What if another huge earthquake strikes? And when will that happen?

More than 30 years ago, a man with a doctorate in zoology thought he knew the answer.

Iben Browning was born in Edna, Texas, in 1918. According to a USGS report published in 1993, he went on to hold more than 60 patents. And he churned out at least four books dealing with “relationships between climate and the affairs of men; robots; and AIDs.”

He worked as a consultant for NASA in the 1960s, once claiming the layer of dust on the moon was too thick for humans to land on it. In later years, he became a well-known climatologist and agricultural business consultant.

And in the mid-1980s, he started kicking around an idea: A large earthquake along the New Madrid system could soon decimate the Midwest.

Could a major earthquake hit Evansville, Indiana?

He claimed the science was on his side. He said stress from tidal loading, in part, could trigger the quake. And as his prediction progressed, he even provided a date of when it could happen: within 48 hours of Dec. 3, 1990.

The media frothed. The Evansville Courier alone published more than 100 articles about Browning in 1990 — about one every three days. The story went worldwide, and as doomsday crept nearer, TV stations and rubberneckers flocked to New Madrid, Missouri, flushing the tiny town with tourism dollars.

Carbondale, Illinois, told city workers not to take vacations around the date. Walmart stores from Arkansas to Indiana sold garbage cans stuffed with essential goods. And on Dec. 3, more than 45 percent of EVSC students were kept home from school, the Courier reported.

Of course, the earthquake never hit. In its 1993 postmortem, the USGS tried to figure out why so many people took the prediction seriously.

As with all misinformation, there were several factors at play. At least one seismologist endorsed Browning’s prediction, penning a memo to regional experts that was eventually picked up by the media. Browning also earned some respect through his job as an environmental consultant.

Then there was Browning’s reputation as a kind of Calamity Nostradamus. He claimed to have predicted both the eruption of Mount St. Helens and the Loma Prieta earthquake before each occurred. But the USGS pored through his remarks and found that he only spoke in generalities or offered hypotheses obvious to anyone with geologic knowledge.

“Although nearly all seismologists rejected Browning's prediction, why were they ineffective in publicly discrediting it?” the USGS wrote. “… What long-term gains and losses for earthquake preparedness have resulted from the Browning episode?”

Between two seismic zones

On April 6, 2009, a magnitude-6.3 earthquake tore through L’Aquila, Italy. More than 300 people died.

No long after, Italian police came knocking on seven scientists’ doors.

The members of the National Commission for the Forecast and Prevention of Major Risks were eventually charged with manslaughter, accused of downplaying the possibility of a quake. In 2012, a judge sentenced the defendants to six years in prison and barred them from ever holding public office again.

The sentences were eventually overturned. But for geologists, the incident “kind of rocked our world,” Doss said.

“The scientific community very simply does not have the ability right now to project when an earthquake of a given magnitude will occur,” he said. “If we pushed that limit of ‘I’m pretty sure this is going to happen and you ought to get the hell out,’ well, everybody gets out except the bad guys and gals and nothing happens. (That could lead) to looting and all that stuff. There are big social implications to that kind of behavior.”

All we know for certain is that Evansville rests in the shadows of two seismic zones. And if the Wabash ever reaches its full potential, a lot of people could suffer.

But the Earth is loaded with weapons. Back in 2016, New Yorker reporter Kathryn Schulz won the Pulitzer Prize for “The Really Big One,” which laid out how an earthquake could wipe out the Western half of America.

People block all that out. You couldn’t live your life if you didn’t. But it’s astonishing to Doss that so few people know, or even care, how this planet works — and are prepared for the consequences.

“There is an absolute lack of awareness about the Earth,” he said. “As I say to my students, how many of those do we have? Oh, that’s right. We have one.”