A rare type of deep underground earthquake occurring in the Earth’s mantle, which can trigger dangerous surface quakes, has finally been isolated and mapped by Stanford researchers.
The earthquakes in question, known as continental mantle quakes, occur in the mantle layer between the crust and the planet’s molten iron core. A recent study, published in Science, and its accompanying mapping of these regions within the Earth, provide important new insights for scientists studying the complex triggers of earthquakes that can devastate human infrastructure.
A Continental Mantle Earthquake Map
The team’s global map of continental-mantle earthquakes reveals that such events tend to cluster regionally. Two of the main hot spots for their activity exist beneath the Himalayas and the Bering Strait, which runs south of the Arctic Circle between Asia and North America.
Providing researchers with new insights into the crust-mantle boundary and the upper mantle’s role in earthquake events, the new data offers scientists a better understanding of the transport of volcanic magma that drives tectonic movements closer to the surface.
“Until this study, we haven’t had a clear global perspective on how many continental mantle earthquakes are really happening and where,” said lead author Shiqi (Axel) Wang, a former PhD student in the lab of geophysics professor Simon Klemperer at the Stanford Doerr School of Sustainability. “With this new dataset, we can start to probe at the various ways these rare mantle earthquakes initiate.”
While earthquakes that occur at shallower depths are typically associated with more direct impacts on our surface environment, the new research suggests that understanding the effects of deeper continental-mantle earthquakes could provide new insights into Earth science and increase our understanding of how surface quakes occur.
“Although we know the broad strokes that earthquakes generally happen where stress releases at fault lines, why a given earthquake happens where it does and the main mechanisms behind it are not well grasped,” added Klemperer, senior study author. “Mantle earthquakes offer a novel way to explore earthquake origins and the internal structure of Earth beyond ordinary crustal earthquakes.”
Our Layered Earth
The mantle and the crust are very different environments. While the crust is relatively cold and brittle, the mantle is warm and soft, extending down for 1,800 miles. The two layers meet in a boundary area called the Mohorovičić discontinuity, or “the Moho.” Researchers debated for decades whether the vicious nature of the mantle would even allow seismic activity.
Typical continental earthquakes occur well above the Moho, only reaching depths of 6 to 18 miles. Subduction zones are outliers, however, whose dense oceanic plates can sometimes push quakes to depths of hundreds of miles. Occasional sensor data suggests that some quakes may run even deeper, perhaps 50 miles below the Moho, and occur not in subduction zones, but under continental land masses.
For the last few decades, researchers have gathered evidence that, on rare occasions (perhaps with only one percent of the frequency of surface quakes), some events can occur within the mantle. However, identification of these events long remained beyond the limits of the sparse data available to researchers.
Identifying Continental Mantle Earthquakes
To address this issue, Wang and Klemperer developed a method that compares two types of seismic waves to distinguish between crustal and mantle earthquakes. One type is the Sn wave, which travels along the mantle lid, and another is the high-frequency Lg wave, which passes through the crust. By comparing wave-size ratios, the pair was successfully able to determine the point of origin for mantle quakes.
“Our approach is a complete game-changer because now you can actually identify a mantle earthquake purely based on the waveforms of earthquakes,” said Wang.
The team collected a trove of data from seismic monitoring stations around the globe and combined it with other information related to factors such as crustal thickness, location of the measurement, and other criteria. From this dataset, they identified 459 continental earthquakes out of 46,000 total quakes that have occurred since 1990.
Understanding Earthquakes
The team notes that many more of these events may be occurring, but simply have not been captured by sensors, and recommends expanding sensor networks into the Tibetan Plateau as a starting point for collecting more data on mantle continental earthquakes.
With the events now discreetly identified thanks to the team’s new method, they plan to follow up by examining each event to determine what, specifically, their underlying cause appears to be. So far, data points to the idea that some are deep aftershocks of crustal quakes, while others may be generated by heat-driven convection as the mantle subducts the Earth’s crust.
“Continental mantle earthquakes might be part of an inherently interconnected earthquake cycle, both from the crust and also the upper mantle,” said Wang. “We want to understand how these layers of our world function as a whole system.”
The paper, “Continental Mantle Earthquakes of the World,” appeared in Science on February 5, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.