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Weak Faults Play a Strong Role in the Tibetan Plateau’s Deformation
As the Indian and Eurasian continental plates collide, the Tibetan Plateau is slowly deforming. For decades, geoscientists debated how this deformation occurs: Is the plateau like a block of crumbly aged cheddar, deforming mostly at its faults, or is it more like French brie, moving like a very viscous liquid being pushed slowly to the east?
A new study published in Science shows that both theories are at work. The study’s findings provide the most comprehensive picture yet of the Tibetan Plateau’s deformation and offer valuable information for earthquake hazard assessments in the region.
The new model that combines the two theories is a “significant advance,” said Eric Fielding, a geodesist who was not involved in the study. Fielding is a staff member at NASA’s Jet Propulsion Laboratory but did not speak on behalf of the agency. “It’s clearly the result of a very large amount of work,” he said.
A Deformation Investigation
For decades, scientists have held differing views on the Tibetan Plateau’s deformation. One camp modeled the plateau’s deformation with movement occurring mostly at its faults, while the other modeled the movement like a thick fluid deforming areas beyond faults.
“These two communities have carried on modeling deformation in different ways” and have never fully resolved the differences between their models, said Tim Wright, a geodesist at the University of Leeds in the United Kingdom and lead author of the new study.
It’s tricky to measure the plateau’s deformation, though, because it changes so slowly: One of the fastest faults on the plateau, the Kunlun Fault, moves at about just 10 millimeters per year. “These are rates that are less than your fingernails growing,” Wright said.
And because much of the Tibetan Plateau’s terrain is inaccessible, there’s a dearth of ground-based stations to track movement, meaning most geodetic data for the area must come from satellites.
“It’s a boon for science to have that consistent acquisition of the same kind of data for 10 years.”
Tracking such nearly imperceptible movement with satellites hundreds of kilometers above requires enormous amounts of data collected over many years. Wright and his colleagues finally had those data after 10 years of observations from the European Space Agency’s Sentinel-1 satellite mission, which launched in 2014.
“Because the signals are so small, you need to wait for some time before you accrue enough deformation that you can actually measure it,” Wright said. The 2014–2024 data they analyzed are “giving us a really clean signal,” he said.
“It’s a boon for science to have that consistent acquisition of the same kind of data for 10 years,” Fielding said.
Using tens of thousands of satellite images alongside ground-based satellite navigation system stations, Wright and the team constructed comprehensive velocity maps of the deformation of the plateau. Results showed that a mix of theories best describes the mechanism.
“We think what’s really happening is a combination of both,” Wright said.
Wright, who described himself as “formerly of the viscous deformation camp,” was surprised by the prominent role that faults played in the plateau’s deformation. Previously, he said, he would have described the faults as passive markers within the underlying flow of the landmass. But the data show that the faults influence a much broader area of the plateau: “The whole deformation of the plateau is influenced by those faults,” he said.
The study “shows clearly that these major fault systems are responsible for a large part of the strain within the plateau,” Fielding said.
Mapping Seismic Hazards
“We have very little information about the history of earthquakes on these faults in this area.”
Knowing how the plateau deforms can also help scientists create more accurate seismic hazard assessments for the millions of people who may be affected by earthquakes there, particularly at the edges of the plateau. “We have very little information about the history of earthquakes on these faults in this area,” Fielding said.
The research team is working with the Global Earthquake Model Foundation, a nonprofit earthquake research collaboration, and other organizations to incorporate their findings into hazard assessments.
Wright and the research team recently used a similar methodology to map the deformation field of the entire Alpine-Himalayan belt, which stretches from Spain to eastern China. The same methods could be used to map the deformation of the western United States, another area where both viscous and fault-related deformation may affect large population centers, Fielding said.
—Grace van Deelen (@gvd.bsky.social), Staff Writer
