Nav: Home

Solved: How tides can trigger earthquakes

June 07, 2019

The tides are turning in a quest to solve an earthquake mystery.

Years ago, scientists realized that earthquakes along mid-ocean ridges -- those underwater mountain ranges at the edges of the tectonic plates -- are linked with the tides. But nobody could figure out why there's an uptick in tremors during low tides.

"Everyone was sort of stumped, because according to conventional theory, those earthquakes should occur at high tides," explained Christopher Scholz, a seismologist at Columbia University's Lamont-Doherty Earth Observatory.

In a study published today in Nature Communications, he and his colleagues have uncovered the mechanism for this seeming paradox, and it comes down to the magma below the mid-ocean ridges.

"It's the magma chamber breathing, expanding and contracting due to the tides, that's making the faults move," said Scholz, who co-led the study along with Lamont-Doherty graduate student Yen Joe Tan.

Going against the tide

The low tide correlation is surprising because of the way the mid-ocean fault moves. Scholz described the fault as a tilted plane that separates two blocks of earth. During movement, the upper block slides down with respect to the lower one. So, scientists expected that at high tides, when there is more water sitting on top of the fault, it would push the upper block down and cause the earthquakes. But that's not what happens. Instead, the fault slips down during low tide, when forces are actually pulling upwards -- "which is the opposite of what you'd expect," said Scholz.

To get to the bottom the mystery, he, Tan, and Fabien Albino from the University of Bristol studied the Axial Volcano along the Juan de Fuca Ridge in the Pacific Ocean. Because the volcano erupts every ten years or so, scientists have set up dense networks of ocean bottom instruments to monitor it. The team used the data from those instruments to model and explore different ways the low tides could be causing the tremors.

In the end, it came down to a component that no one else had considered before: the volcano's magma chamber, a soft, pressurized pocket below the surface. The team realized that when the tide is low, there is less water sitting on top of the chamber, so it expands. As it puffs up, it strains the rocks around it, forcing the lower block to slide up the fault, and causing earthquakes in the process.

Furthermore, said Scholz, the tidal earthquakes in this region are "so sensitive that we can see details in the response that nobody could ever see before." When the team charted the earthquake rate versus the stress on the fault, they realized that even the tiniest stress could trigger an earthquake. The tidal data helped to calibrate this effect, but the triggering stress could be caused by anything -- such as the seismic waves from another earthquake, or fracking wastewater pumped into the ground.

"People in the hydrofracking business want to know, is there some safe pressure you can pump and make sure you don't produce any earthquakes?" said Scholz. "And the answer that we find is that there isn't any -- it can happen at any level of stress."

Of course, a small stress over a small area isn't going to cause a devastating earthquake, and the exact amount of stress needed varies from place to place. "Our point is there's no intrinsic stress that has to be exceeded to cause an earthquake," says Scholz. "There isn't any rule of thumb."
-end-
Contact: Christopher Scholz
scholz@ldeo.columbia.edu
(845) 365-8360

Lamont-Doherty Earth Observatory is Columbia University's home for Earth science research. Its scientists develop fundamental knowledge about the origin, evolution and future of the natural world, from the planet's deepest interior to the outer reaches of its atmosphere, on every continent and in every ocean, providing a rational basis for the difficult choices facing humanity. http://www.ldeo.columbia.edu | @LamontEarth

The Earth Institute, Columbia University mobilizes the sciences, education and public policy to achieve a sustainable earth. http://www.earth.columbia.edu.

Earth Institute at Columbia University

Related Stress Articles:

Captive meerkats at risk of stress
Small groups of meerkats -- such as those commonly seen in zoos and safari parks -- are at greater risk of chronic stress, new research suggests.
Stress may protect -- at least in bacteria
Antibiotics harm bacteria and stress them. Trimethoprim, an antibiotic, inhibits the growth of the bacterium Escherichia coli and induces a stress response.
Some veggies each day keeps the stress blues away
Eating three to four servings of vegetables daily is associated with a lower incidence of psychological stress, new research by University of Sydney scholars reveals.
Prebiotics may help to cope with stress
Probiotics are well known to benefit digestive health, but prebiotics are less well understood.
Building stress-resistant memories
Though it's widely assumed that stress zaps a person's ability to recall memory, it doesn't have that effect when memory is tested immediately after a taxing event, and when subjects have engaged in a highly effective learning technique, a new study reports.
Stress during pregnancy
The environment the unborn child is exposed to inside the womb can have a major effect on her or his development and future health.
New insights into how the brain adapts to stress
New research led by the University of Bristol has found that genes in the brain that play a crucial role in behavioural adaptation to stressful challenges are controlled by epigenetic mechanisms.
Uncertainty can cause more stress than inevitable pain
Knowing that there is a small chance of getting a painful electric shock can lead to significantly more stress than knowing that you will definitely be shocked.
Stress could help activate brown fat
Mild stress stimulates the activity and heat production by brown fat associated with raised cortisol, according to a study published today in Experimental Physiology.
Experiencing major stress makes some older adults better able to handle daily stress
Dealing with a major stressful event appears to make some older adults better able to cope with the ups and downs of day-to-day stress.

Related Stress Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#529 Do You Really Want to Find Out Who's Your Daddy?
At least some of you by now have probably spit into a tube and mailed it off to find out who your closest relatives are, where you might be from, and what terrible diseases might await you. But what exactly did you find out? And what did you give away? In this live panel at Awesome Con we bring in science writer Tina Saey to talk about all her DNA testing, and bioethicist Debra Mathews, to determine whether Tina should have done it at all. Related links: What FamilyTreeDNA sharing genetic data with police means for you Crime solvers embraced...