A hidden lubricant in creeping faults? Uncovering the mysteries of aseismic slip

Geological faults hold many secrets that may help us answer important questions about the nature of our planet and what really happens deep underground. One of the biggest mysteries lies within the Atotsugawa Fault System in Japan. What makes the area unusual is that, despite being in a tectonically active region where Earth's plates are constantly shifting, it does not produce as many large earthquakes as other major faults.

A group of researchers at Tohoku University has shed light on an unknown aspect of the Atotsugawa Fault System, revealing why earthquakes are unusually rare there. Using an innovative approach that combines advanced analytical techniques such as Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopy (TEM), they made an intriguing discovery: a single layer of graphene oxide found within this active fault may be the key to solving this mystery.

What makes this discovery particularly significant is that graphene oxide, widely used in cutting-edge technology and typically produced synthetically, has not been observed naturally in such an ultrathin form before. In this setting, it exhibits unique properties, including an extremely smooth surface that leads to very low friction. The presence of this natural lubricant may help explain why some faults move slowly and steadily rather than causing sudden earthquakes.

In their research, the team focuses on two key mechanisms that reduce friction in faults. First, oxygen-containing groups in graphene oxide interact with water molecules, creating lubricating conditions. Second, graphene oxide nanosheets slide between minerals in the fault, reducing friction even more.

"We believe that when faults move, they trigger chemical reactions that create graphene oxide. In other words, the more a fault slips, the more it generates its own 'nano-lubricant,' which helps the fault move even more easily," said Professor Hiroyuki Nagahama.

This study suggests that graphene oxide can remain stable under the temperature conditions present at depths where slow fault slip occurs. This implies that once formed, it may continue to act as a natural lubricant over long periods of time, influencing how stress is released along the fault. These findings highlight the previously unrecognized role of carbon-based materials in regulating fault behavior.

"If graphene oxide can form naturally in faults, it opens up entirely new possibilities－not only for understanding earthquake behavior, but also for exploring how faults evolve over time," said Tomoya Shimada, a member of the research team from the Department of Earth Science at Tohoku University.

Ultimately the discovery elucidates more about fault behavior while also highlighting the power of interdisciplinary research to uncover hidden processes within the Earth. Studies like these, which bridge the gap between geoscience, materials science, and tribology, have the potential to fundamentally transform how carbon is studied on Earth. As research continues, these approaches may help deepen our understanding of earthquake processes and how faults behave deep underground.

The findings were published in Nature Communications on May 12, 2026.