Sarah Stamps, using 3D thermal modeling, came up with research led by Dr. This adds complexity to the debate about the initial forces driving the rift, suggesting a combination of buoyancy in the lithosphere and mantle traction.
Computer simulations confirmed that the African superelement causes unusual deformations and seismic anisotropy parallel to the faults detected under the East African Rift System.
Geophysicist Dr. This process is related to the elongation of the lithosphere, the Earth’s hard outer layer. As the lithosphere becomes denser, the upper part of the lithosphere undergoes a brittle change, which causes cracks in the rock and earthquakes.
Stamp, who studied this process using computer modeling and GPS to map surface motion to millimeter precision, compares the different deformation patterns of the fractured continents by playing a game of goofy putty.
“If you hit cellulite putty with a hammer, it can crack and break,” said Stamps, a professor in the Department of Earth Sciences, part of Virginia Tech’s College of Science. “But if you loosen it slowly, the silly putty will expand. So on different time scales, Earth’s lithosphere behaves differently.”
Whether expanding or breaking apart, the deformation that comes with a continental rift usually follows a predictable directional pattern with respect to the rift: the deformation tends to be perpendicular to the rift. The East African Rift System, the largest continental rift system on Earth, has this vertical deformation. But after measuring the fault system with GPS instruments for more than 12 years, Stamps also noticed deformations in the opposite direction, parallel to the system faults. His team at the Laboratory of Geodesy and Tectonic Physics are working to find out why.
Assistant Professor Dr. Sarah’s stamp. Credit: Virginia Tech
In a recent study published in Geophysical Research Journal, the team explores the processes behind the East African Rift System using 3D thermal modeling developed by the study’s first author, Tahiri Rajaonarisson, a postdoctoral researcher at New Mexico Tech who received his Ph.D. at Virginia Tech as a member of the Stamps Lab. Her model suggests that the parallel rift deformation of the rift system is driven by northward mantle flows associated with the Great African Surface, the massive uplift of the mantle that rises from the depths of the Earth beneath southwest Africa and extends northeast across the continent, becoming shallower. . Because it extends north.
Their findings, combined with insights from a study the researchers published in 2021 using the Rajaonarisson modeling technique, can help clarify the scientific debate about which plate driving forces dominate the East African Rift System, explaining both perpendicular deformation and parallel cracking. . Buoyancy in the lithosphere, drag in the mantle, or both.
As a postdoctoral researcher, Stamps began observing the East African system’s unusual parallel rift deformation using data from GPS stations measuring signals from more than 30 satellites orbiting Earth, from a distance of about 25,000 kilometers. His observations have added another layer of complexity to the debate about what drives system errors.
Some scientists theorize that the East Africa Rift is primarily driven by buoyant forces in the lithosphere, which are relatively shallow forces mainly caused by the high topography of the rift system, known as the African Superwell, and the density differences in the lithosphere. Others point to horizontal mantle drag, deeper forces arising from interactions with the mantle flowing horizontally beneath East Africa, as the underlying thrust.
tim Study 2021 He found through 3D computer simulations that the cracks and their deformations could be driven by the combination of the two forces. Their model suggests that buoyant forces in the lithosphere are responsible for the more predictable vertical rift deformation, but these forces cannot explain the anomalous deformation parallel to the fault captured by GPS Stamps measurements.
In the newly published study, Rajaonarison again uses 3D thermomechanical modeling, this time to focus on sources of deformation parallel to the cracks. His models confirmed that the African super plume is responsible for the unusual deformation as well as the seismic anisotropy that parallels the faults observed under the East African Rift System.
Seismic anisotropy is the orientation or alignment of rocks in a particular direction in response to mantle flows, melt pockets, or pre-existing structures in the lithosphere, Stamps said. In this case, the alignment of the rocks follows northward of the major African mantle flows, indicating the mantle flows as their source.
“We say that mantle flow does not drive orthogonal east-west rifts of multiple deformations, but can cause deformations parallel to the north that are parallel to rifts,” Rajaonarisson said. “We have confirmed previous ideas that buoyancy in the lithosphere drives the rift, but we provide new insights that abnormal deformation can occur in East Africa.”
Knowing more about the processes involved in continental rift, including anomalous ones, will help scientists untangle the complexities behind continental rift, something they have been trying for decades. “We are very pleased with the results of Dr. This Rajaonarison is because it provides new information about the complex processes that shape the Earth’s surface through continental rifts,” said Stamps.
Reference: “Geodynamic Investigations of Lithosphere and Feather Interactions Beneath the East African Rift” by Taheri A. Rajaonarison and Dr. Sarah Stamps, John Nalipov, Andrew Nibbled, and Emmanuelle A. Journal of Geophysics Research, Solid Earth.
doi: 10.1029/2022JB025800
2023-08-17 05:17:52
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