A rare and mysterious type of earthquake that occurs deep in the Earth’s crust has been discovered by scientists

A rare type of deep underground earthquake that occurs in the Earth’s mantle, and which can trigger dangerous surface quakes, has finally been isolated and mapped by researchers at Stanford University.

The earthquakes in question, known as continental mantle earthquakes, occur in the mantle between the crust and the planet’s molten iron core. A recent study, published in the journal Science, and its accompanying mapping of these regions within the Earth, provide important new insights for scientists studying the complex etiology of earthquakes that can damage human infrastructure.

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 hotspots of their activity are under the Himalayas and the Bering Strait, which runs south of the Arctic Circle between Asia and North America.

The new data provides researchers with new insights into the crust-mantle boundary and the role of the upper mantle in earthquake events, and provides scientists with a better understanding of the transport of volcanic magma that drives tectonic movements near the surface.

“Until this study, we did not have a clear global perspective on how many continental mantle earthquakes actually occur and where,” said lead author Shiqi (Axel) Wang, a former doctoral student in the lab of geophysics professor Simon Klemperer at Stanford’s Doerr School of Sustainability. “With this new dataset, we can begin to explore the different ways rare mantle earthquakes initiate.”

While earthquakes that occur at shallower depths are typically associated with more direct impacts on our surface environment, new research suggests that understanding the effects of earthquakes deep in the continental mantle could provide new insights into Earth sciences and increase our understanding of how surface earthquakes occur.

“Although we know the broad strokes along which earthquakes generally occur when stress is released at fault lines, why a particular earthquake occurs where it does and the key mechanisms behind it are not well understood,” added Klemperer, the study’s senior author. “Mantle earthquakes offer a new way to explore the origins of earthquakes and the Earth’s internal structure beyond ordinary crustal earthquakes.”

For the first time, researchers have been able to map continental mantle earthquakes. Credit: Axel Wang Our Layered Earth

The mantle and the crust are two completely different environments. While the crust is cold and relatively fragile, the mantle is warm and soft, extending downward for 1,800 miles. The two layers meet in a border area called the Mohorovičić discontinuity, or “the Moho.” Researchers have debated for decades whether the mantle’s sinister nature would allow seismic activity to occur.

Typical continental earthquakes occur above the Moho River, reaching depths of only 6 to 18 miles. However, subduction zones are extreme zones, whose dense oceanic plates can sometimes push earthquakes to depths of hundreds of miles. Occasional sensing data suggests that some of the earthquakes may be deeper, perhaps as deep as 50 miles beneath the Moho, and occur not in subduction zones, but beneath continental land masses.

Over the past few decades, researchers have collected evidence that on rare occasions (perhaps only one percent of the frequency of surface earthquakes), some events can occur within the mantle. However, identifying these events has long remained beyond the sparse data available to researchers.

Identifying continental mantle earthquakes

To address this problem, 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, and the other is the high-frequency Lg wave, which passes through the crust. By comparing wave size ratios, the pair succeeded in pinpointing the point of origin of mantle earthquakes.

“Our approach is completely game-changing because you can now identify a mantle earthquake based on the earthquake waveforms,” ​​Wang said.

The team collected a range of data from earthquake monitoring stations around the world and combined it with other information related to factors such as crustal thickness, measurement location, and other parameters. From this data set, they identified 459 continental earthquakes out of 46,000 total earthquakes that have occurred since 1990.

Understanding earthquakes

The team notes that many of these events may be occurring, but simply not captured by sensors, and recommends expanding sensor networks in the Tibetan Plateau as a starting point for collecting more data on continental earthquakes in the mantle.

With events now confidentially identified thanks to the team’s new method, they plan to follow up by examining each event to specifically determine the root cause. So far, the data point to the idea that some are deep aftershocks from crustal earthquakes, while others may be generated by convection generated by heat as the mantle sinks into the Earth’s crust.

“Continental mantle earthquakes may be part of an inherently interconnected seismic cycle, both from the crust and also from the upper mantle,” Wang said. “We want to understand how these layers of our world function as a whole system.”

The paper, “The world’s continental mantle earthquakes,” appeared in the journal Science on February 5, 2026.

Ryan Whalen covers science and technology for The Debrief. He holds a Master’s degree in History and a Master’s in Library and Information Science with a certificate in Data Science. He can be contacted at [email protected], and followed on Twitter @mdntwvlf.

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