Wash U seismologist sees no indication big St. Louis earthquake is likely – but doesn't rule it out | St. Louis Public Radio

Wash U seismologist sees no indication big St. Louis earthquake is likely – but doesn't rule it out

Jan 2, 2019

Michael Wysession is a professor of seismology in Washington University's Department of Earth and Planetary Sciences.
Credit Evie Hemphill | St. Louis Public Radio

Last month’s 4.4 magnitude earthquake in Tennessee set off fresh questions about the potential for significant seismic activity occurring in the St. Louis region, which last saw earthquakes of magnitude 7 or larger in the early 19th century.

According to the Missouri Department of Natural Resources, the New Madrid Seismic Zone “appears to be about 30 years overdue” for a magnitude 6.3 quake. But on Wednesday’s St. Louis on the Air, Washington University Professor of Seismology Michael Wysession suggested that a focus on flooding and tornadoes remains appropriate when it comes to disaster preparedness in the region.

“Based on the seismicity that we see happening today, we don’t see any indication that there will be a large one, of that scale [magnitude 6 or 7], anytime in the near future,” Wysession told host Don Marsh.

Still, he was quick to add that a “big one” isn’t out of the question.

“Straight off, let me say: No one knows. And it’s a little embarrassing, as a scientist, not to be able to answer that question,” said Wysession. “If I studied volcanoes, because of the way that volcanoes occur with magma cracking its way to the surface, releasing gases causing higher temperatures, I might be able to predict a volcanic eruption down to a day. That has been done in the past. The way an earthquake occurs is very different.

“Imagine taking a pencil and bending it and bending it until it snapped. You might not know anything about when that snap would occur until it actually happened. It’s the last straw that breaks the camel’s back. And often, for many earthquakes, we get no warning before that earthquake occurs. So we’ve not been able to predict earthquakes, and we’ve even found the forecasting based on probability to be very challenging, because it’s not like the seasons or day and night where you can predict exactly where winter and summer are going to occur.”

The seismologist added that even in regions that have had earthquakes going back “as far as we have human history,” their occurrence is far from regular.

“So we can’t tell you, unfortunately, when the next large earthquake would occur,” he explained.

When asked about the level of risk the St. Louis region would face in terms of infrastructure impact and loss of life from any earthquakes associated with the New Madrid Seismic Zone, Wysession said the Gateway City is “in a pretty good place.”

“We do have historical evidence from 1811 and 1812 [earthquakes], because there were over 5,000 people living in the St. Louis region at the time, and there were structures and buildings, and when those earthquakes occurred, some loose chimneys fell down,” he said. “There was not much damage beyond that. But we also didn’t [yet] have skyscrapers.”

He added that determining such risk isn’t as simple as considering the distance from the seismic zone.

“It’s interesting, because there were places half the distance to New Madrid – still right along the Mississippi River, places like Ste. Genevieve – where not a pane of glass broke and not a brick fell from those earthquakes [in 1811 and 1812],” Wysession said. “So the way the seismic waves propagate is also not simply a function of distance. It’s a function of the type of rock underneath, and it’s a process, we have learned since being able to examine large earthquakes elsewhere, of the focusing and defocusing of the seismic waves.”

St. Louis on the Air brings you the stories of St. Louis and the people who live, work and create in our region. St. Louis on the Air host Don Marsh and producers Alex HeuerEvie Hemphill and Lara Hamdan give you the information you need to make informed decisions and stay in touch with our diverse and vibrant St. Louis region.