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Slow-motion earthquakes, as you might guess from the name, involve the release of pent-up geological energy over the course of days or weeks rather than minutes – and scientists have now recorded some as they were happening.

These quakes, also known as slow slip earthquakes or just slow earthquakes, are typically too gentle to cause immediate danger. However, they can help scientists predict full-speed earthquakes or tsunamis, which can of course be far more dangerous.

A team led by researchers from the University of Texas Institute for Geophysics (UTIG) tracked two separate slow slip events (SSEs) in real time – one in 2015 and another in 2020.

Special borehole sensors were positioned deep underwater, close to the Nankai Trough subduction zone off the coast of Japan. There, the Philippine Sea plate is pushing under the Eurasian plate. The researchers describe the activity of the slow quakes as being like a tectonic shock absorber.

“It’s like a ripple moving across the plate interface,” says hydrogeophysicist Josh Edgington, from UTIG.

Related: Earthquakes Today Could Be Echoes of Powerful Quakes Centuries Ago

The measurements confirm what scientists had previously thought about these slow-motion earthquakes, which were only recently discovered: that they can be significant in releasing (or building) stress around a faultline.

This subduction zone is part of the Pacific Ring of Fire, an extensive collection of volcanoes and faults surrounding the Pacific Ocean. It’s responsible for many of the largest earthquakes and tsunamis on record.

And the findings here, about the shock absorber effect, will be crucial in understanding when and where future earthquakes could hit. Other faults lack this kind of tectonic protection, including Cascadia off the western coast of North America.

“This is a place that we know has hosted magnitude 9 earthquakes and can spawn deadly tsunamis,” says geophysicist Demian Saffer, from UTIG. “Are there creaks and groans that indicate the release of accumulated strain, or is the fault near the trench deadly silent?”

“Cascadia is a clear top-priority area for the kind of high-precision monitoring approach that we’ve demonstrated is so valuable at Nankai.”

It’s only possible to measure these SSEs because of advances in sensor technology, meaning shakes of much lower strength – sometimes only shifting the ground a few millimeters at a time – can be detected.

Through their analysis, the researchers were able to determine that slow earthquakes may be related to high geologic fluid pressures, and that the upper part of the fault can release pressure independently of the rest of it.

All of this helps to inform models predicting earthquakes and tsunamis – with the potential to save thousands of lives. The last major Nankai Trough quake happened in 1946, with the loss of tens of thousands of properties and causing more than 1,300 deaths.

Predicting earthquakes isn’t an exact science, with a host of variables involved, but it’s something we’re getting better at. With each study and technological upgrade, seismologists are improving their models, and adding in data from slow earthquake activity could help greatly.

“The patterns of strain accumulation and release along the offshore reaches of subduction megathrusts are particularly important toward understanding hazards associated with shallow coseismic slip and tsunamigenesis,” write the researchers in their published paper.

The research has been published in Science.

KNOXVILLE, TN, July 08, 2025 /24-7PressRelease/ — Researchers explore how 6-PPD quinone (6-PPDQ), an environmental contaminant derived from tire antioxidant N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD), affects the citric acid cycle in C. elegans at environmentally relevant concentrations. The research reveals significant reduction in the citric acid cycle intermediates and key enzyme gene expressions by 6-PPDQ exposure, highlighting the its potential exposure risk on citric acid cycle metabolism.

6-PPDQ, has emerged as an environmental concern due to its widespread detection and toxic effects. In a study published in Environmental Chemistry and Ecotoxicology, researchers from Southeast University in China explored the effects of 6-PPDQ on the citric acid cycle and underlying mechanism in C. elegans. The citric acid cycle, a crucial metabolic pathway occurring in the mitochondria, plays a central role in cellular metabolism by linking carbohydrate, fat, and amino acid metabolisms. It provides intermediates for the synthesis of amino acids, fatty acids, and glycogen, which are essential for sustaining life activities.

The study reveals how 6-PPDQ at environmentally relevant concentrations (0.1–10 μg/L) disrupted the citric acid cycle by reducing intermediate metabolites, including citric acid, α-ketoglutarate, succinate, fumarate, malate, and oxaloacetate. Additionally, the reduction of these intermediate metabolites was due to the inhibition of relevant key enzyme gene expressions. Exposure to 6-PPDQ suppressed genes encoding citrate synthase (cts-1), isocitrate dehydrogenase 2 (idh-2), and α-ketoglutarate dehydrogenase complex (dlst-1, dld-1). As explained by the researchers, “exposure to 6-PPDQ significantly impacts the citric acid cycle in C. elegans, which is crucial for understanding the potential risks of this contaminant to both environmental and human health.”

The researchers also observed that 6-PPDQ exposure decreased acetyl CoA and pyruvate contents, which are important for the control of citric acid cycle. Acetyl CoA generated from pyruvate is a key substrate for the cycle. The study found that among the genes encoding components of the pyruvate dehydrogenase complex, which controls acetyl CoA synthesis, only dlat-1 and dld-1 expressions were decreased by 6-PPDQ. The expressions of genes pyk-1 and pyk-2 associated with pyruvate generation were also reduced. RNA interference (RNAi) of these genes further exacerbated the cycle’s disruption, highlighting the crucial contribution of these alterations to 6-PPDQ-induced toxicity.

The study also demonstrated that the disruption in citric acid cycle and reduction in acetyl CoA and pyruvate contents contributed to mitochondrial dysfunction, as indicated by increased oxygen consumption rates and decreased ATP content in 6-PPDQ exposed nematodes. Furthermore, the researchers investigated the protective effects of sodium pyruvate treatment, finding that it could suppress toxic effects of 6-PPDQ. “Our results suggest that sodium pyruvate treatment may be a promising approach to against 6-PPDQ toxicity,” the researchers concluded.

This study provides valuable insights into the mechanisms by which 6-PPDQ disrupts metabolic process of citric acid cycle and highlights the potential risks of this contaminant. The findings underscore the importance of further research to fully understand the implications of 6-PPDQ exposure for both environmental and human health.

References

DOI

10.1016/j.enceco.2025.05.022

Original Source URL

https://doi.org/10.1016/j.enceco.2025.05.022

Journal

Environmental Chemistry and Ecotoxicology

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