New technique uses earth’s surface to reveal its hidden interior

A GPS station atop the Sierra Nevada mountains. UT Austin researchers used GPS networks to image the planet’s interior. Credit: UNAVCO/NSF.

Scientists at The University of Texas at Austin have developed a groundbreaking technique that uses surface mapping technology to look inside the Earth.

This new method, called “deformation imaging,” allows researchers to gather detailed information about the rigidity of the Earth’s crust and mantle, which is crucial for understanding earthquakes and other large geological processes.

Simone Puel, who developed this method during her graduate studies at the UT Jackson School of Geosciences, explains that knowing the material properties like rigidity is essential for studying areas where tectonic plates collide or for understanding earthquake science in general.

Puel is now a postdoctoral scholar at the California Institute of Technology.

Traditional methods like GPS, radar, and laser scanning have long been used to measure the Earth’s surface features.

Now, with this new technique, scientists can use these technologies to get a glimpse of what’s happening beneath the surface. Deformation imaging provides results similar to seismic imaging but gives direct information about the Earth’s rigidity.

Puel’s theory was published in the Geophysical Journal International earlier this year.

A recent study in Science Advances demonstrates the technique in action, using GPS data from Japan’s 2011 Tohoku earthquake.

The method successfully imaged the subsurface down to about 100 kilometers, revealing tectonic plates and volcanic systems beneath Japan. Notably, it detected a deep magma reservoir feeding the volcanic system, marking the first time such a reservoir has been identified using only surface information.

The technique works because the Earth’s crust is made up of rocky materials with different elastic properties—some parts are more flexible, while others are more rigid. This causes the crust to expand and contract unevenly. During an earthquake, these vibrations reflect the composition of the Earth’s interior, deforming the surface in specific ways.

Researchers created a computer model treating the Earth as a simplified elastic material, allowing its strength to vary in three dimensions. By analyzing how much GPS sensors moved during the earthquake, they computed the subsurface rigidity, creating a 3D image of the Earth’s interior based on surface changes.

One significant advantage of this method is that it can use satellite measurements. NASA’s upcoming NISAR spacecraft, a joint mission with the Indian Space Research Organization, will map the entire globe in high resolution every 12 days. Using deformation imaging, NISAR could provide critical insights into some of the world’s most geologically hazardous regions.

Study co-author Thorsten Becker, a professor at the Jackson School, notes that continuously mapping the Earth’s surface with NISAR will allow scientists to track structural changes in earthquake faults over time. This new technique opens up exciting possibilities for understanding and predicting geological events, offering a comprehensive view of the Earth’s hidden interior.