An Earthquake Hazard Where We Least Expect It
In the long term, a life-changing earthquake in America's heartland is almost certainly inevitable.
This article originally appeared in the Newton blog on RealClearScience. You can read the original here.
Between December 16th, 1811 and February 7th, 1812, four earthquakes -- each roughly comparable to San Francisco's legendary rumble in 1906 -- shook the states of Arkansas, Missouri, Illinois, Tennessee, Indiana, Kentucky, and Mississippi. Witnesses painted a cataclysmic picture. In many places, the ground upheaved as if giant burrowing worms tore through the soil. Sections of the mighty Mississippi briefly flowed backwards. River tsunamisspawned and battered the surrounding terrain. Sand volcanoes erupted from the ground.
And yet, despite the terrestrial carnage, loss of life during the four seismic events was small,likely no more than two hundred. If just one of those earthquakes were to strike today, we would not be so lucky.
In 2008, University of Illinois seismologists estimated the toll. Such a disaster would likely result in 86,000 casualties, 715,000 damaged buildings, and 7.2 million people displaced. Direct economic losses would tally at least $300 billion. In short, it would be the most devastating natural disaster in modern history.
But that won't happen, right?
Since the 1811-1812 earthquakes, there have literally been thousands of earthquakes in the New Madrid Seismic Zone, the fault system responsible. But while these may register on the sensitive Richter Scale, the quakes are hardly discernible above ground. This has prompted some seismologists to hypothesize that that these quakes are little more than aftershocks of the 1811-1812 incidents, and that the New Madrid Seismic Zone is, for all intents and purposes, defunct. Many scientists with the United States Geological Survey aren't so sure, however. Fault zones don't simply shut off over two hundred years -- really a blink of an eye in geological terms.
New research backs their majority opinion. Cal Tech seismologists Morgan Page and Susan Hough tallied New Madrid's known seismic activity since 1812 and found that it doesn't fit in with the commonly accepted epidemic-type aftershock model. In other words, the tiny earthquakes the region has produced in the past two hundred years are likely not aftershocks. This is bad news, as aftershocks help relieve stress in a fault system.
"If current seismicity in the New Madrid region is not composed predominately of aftershocks, there must be continuing strain accrual," Page and Hough write in their paper, published in today's issue of Science. That's a sign that the fault system still poses a hazard.
Unlike the notoriously active San Andreas Fault in California, where two enormous continental plates border and occasionally grind together, New Madrid is far away from any tectonic boundary. Therefore, the cause of its earthquakes -- termed "intraplate earthquakes" -- is less understood. (Above image: Intraplate earthquakes often affect a vaster area.)
One potential explanation is that the crust upon which New Madrid rests was previously weakened hundreds of millions of years ago, and thus is now sensitive to subtle shifts in the Earth's plates. 550 million years ago, the crust and lithosphere began to pull apart in that area -- a rift started forming. However, for unknown reasons, the rift failed and subsequently became filled with sediment. Now, we contend with its muffled, earth-shaking temper tantrums.
Thankfully, the odds are decent, at least in our lifetime, that the Central U.S. won't experience a large seismic outburst. The USGS estimates the chance of a magnitude 7.5 event or higher in the next 50 years at about 7 to 10 percent, and the chance of a magnitude 6 or larger earthquake at 25 to 40 percent.
But in the long term, a life-changing earthquake in America's heartland is almost certainly inevitable.
Source: Morgan T. Page and Susan E. Hough. "The New Madrid Seismic Zone: Not Dead Yet."Science (2014)
(Images: AP, USGS)
What can 3D printing do for medicine? The "sky is the limit," says Northwell Health researcher Dr. Todd Goldstein.
- Medical professionals are currently using 3D printers to create prosthetics and patient-specific organ models that doctors can use to prepare for surgery.
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- Northwell Health, New York State's largest health care provider, is pioneering 3D printing in medicine in three key ways.
Great ideas in philosophy often come in dense packages. Then there is where the work of Marcus Aurelius.
- Meditations is a collection of the philosophical ideas of the Roman Emperor Marcus Aurelius.
- Written as a series of notes to himself, the book is much more readable than the dry philosophy most people are used to.
- The advice he gave to himself 2,000 years ago is increasingly applicable in our hectic, stressed-out lives.
Can dirt help us fight off stress? Groundbreaking new research shows how.
- New research identifies a bacterium that helps block anxiety.
- Scientists say this can lead to drugs for first responders and soldiers, preventing PTSD and other mental issues.
- The finding builds on the hygiene hypothesis, first proposed in 1989.
Are modern societies trying too hard to be clean, at the detriment to public health? Scientists discovered that a microorganism living in dirt can actually be good for us, potentially helping the body to fight off stress. Harnessing its powers can lead to a "stress vaccine".
Researchers at the University of Colorado Boulder found that the fatty 10(Z)-hexadecenoic acid from the soil-residing bacterium Mycobacterium vaccae aids immune cells in blocking pathways that increase inflammation and the ability to combat stress.
The study's senior author and Integrative Physiology Professor Christopher Lowry described this fat as "one of the main ingredients" in the "special sauce" that causes the beneficial effects of the bacterium.
The finding goes hand in hand with the "hygiene hypothesis," initially proposed in 1989 by the British scientist David Strachan. He maintained that our generally sterile modern world prevents children from being exposed to certain microorganisms, resulting in compromised immune systems and greater incidences of asthma and allergies.
Contemporary research fine-tuned the hypothesis, finding that not interacting with so-called "old friends" or helpful microbes in the soil and the environment, rather than the ones that cause illnesses, is what's detrimental. In particular, our mental health could be at stake.
"The idea is that as humans have moved away from farms and an agricultural or hunter-gatherer existence into cities, we have lost contact with organisms that served to regulate our immune system and suppress inappropriate inflammation," explained Lowry. "That has put us at higher risk for inflammatory disease and stress-related psychiatric disorders."
University of Colorado Boulder
This is not the first study on the subject from Lowry, who published previous work showing the connection between being exposed to healthy bacteria and mental health. He found that being raised with animals and dust in a rural environment helps children develop more stress-proof immune systems. Such kids were also likely to be less at risk for mental illnesses than people living in the city without pets.
Lowry's other work also pointed out that the soil-based bacterium Mycobacterium vaccae acts like an antidepressant when injected into rodents. It alters their behavior and has lasting anti-inflammatory effects on the brain, according to the press release from the University of Colorado Boulder. Prolonged inflammation can lead to such stress-related disorders as PTSD.
The new study from Lowry and his team identified why that worked by pinpointing the specific fatty acid responsible. They showed that when the 10(Z)-hexadecenoic acid gets into cells, it works like a lock, attaching itself to the peroxisome proliferator-activated receptor (PPAR). This allows it to block a number of key pathways responsible for inflammation. Pre-treating the cells with the acid (or lipid) made them withstand inflammation better.
Lowry thinks this understanding can lead to creating a "stress vaccine" that can be given to people in high-stress jobs, like first responders or soldiers. The vaccine can prevent the psychological effects of stress.
What's more, this friendly bacterium is not the only potentially helpful organism we can find in soil.
"This is just one strain of one species of one type of bacterium that is found in the soil but there are millions of other strains in soils," said Lowry. "We are just beginning to see the tip of the iceberg in terms of identifying the mechanisms through which they have evolved to keep us healthy. It should inspire awe in all of us."
Check out the study published in the journal Psychopharmacology.
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