Researchers Discover Massive Series of Rips in Mantle Under Tibet

By combining new computer modeling technology with older geo data, researchers uncovered answers to some of Tibet's mysterious geological history.

The mantle under Tibet could have a few new tears in it, according to a new computer model. Researchers from the University of Illinois have used an advanced computer modeling system to give geologists and seismologists a unique look at what could be going on underneath our planet's surface. 

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The team, led by the geology department at the University, wanted to discover more about the mysterious history of the Tibetan Plateau and see what future it could have with regard to seismic activity. The region is not one traditionally researched by geologists, the Illinois team noted. The Indian and Asian tectonic plates collided over 50 million years ago, and very little has been done in the way of understanding precisely what happened and how it shaped the current state of the continent until now. 

“The continental collision between the Indian and Asian tectonic plates shaped the landscape of East Asia, producing some of the deadliest earthquakes in the world,” said Xiaodong Song, a geology professor at the University of Illinois and co-author of the new study. “However, the vast high plateau is largely inaccessible to geological and geophysical studies.”

Song and his team discovered the upper mantle layer has been torn into four large pieces diving under Asia. Each mantle piece juts out at a different angle and distance from the origin of the tear itself. 

The team used several sources to create extensive tomographic images of Tibet, and the depth of those images reached nearly 160 kilometers deep. The team then compared the images rendered by the computer modeling system alongside historic earthquake data and other geochemical research conducted in the area. 

“The presence of these tears helps give a unified explanation as to why mantle-deep earthquakes occur in some parts of southern and central Tibet and not others.”

“The presence of these tears helps give a unified explanation as to why mantle-deep earthquakes occur in some parts of southern and central Tibet and not others,” Song said.

Those places of crust between the tears could gather enough strain to generate earthquakes, the researchers noted. The crustal areas above the torn pieces of mantle take more heat and are thus more flexible and pliant. That ability to flex with ease actually makes the warmer crust less likely to have earthquakes as it can absorb the shock of tectonic movement. 

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“What were previously thought of as unusual locations for some of the intercontinental earthquakes in the southern Tibetan Plateau seem to make more sense now after looking at this model,” said graduate student and co-author Jiangtao Li. “There is a striking correlation with the location of the earthquakes and the orientation of the fragmented Indian upper mantle.”

The researchers also discovered the history behind the deformation patterns seen at the surface of Tibet. The country and surrounding area has several north-south rifts. The team juxtaposed their renderings with earthquake locations and deformation patterns to reveal a very strongly coupled crust and upper mantle in the southern part of Tibet. 

“Overall, our new research suggests that we need to take a deeper view to understand the Himalayan-Tibetan continental deformation and evolution,” Song said.

The research has been published in PNAS.

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