High resolution illumination from Earth’s interior to the planet’s core

news/tmb/2022/planet-scale-mri.jpg" data-src="https://scx2.b-cdn.net/gfx/news/2022/planet-scale-mri.jpg" data-sub-html="Azimuthal anisotropy (black dashed lines showing the fast direction of wave speeds) in the mantle at 200 km depth plotted on top of vertically polarized shear wave speed perturbations (dVsv) after 20 iterations based on global azimuthally anisotropic adjoint tomography. The maximum peak-to-peak anisotropy is 2.3%. Red and blue colors denote the slow and fast shear wave speeds with respect to the mean model which are generally associated with hot and cold materials, respectively. Credit: Ebru Bozdag, Colorado School of Mines">

The azimuth contrast (dotted black line indicating a fast wave velocity trend) in the mantle at a depth of 200 km is plotted over the disturbance of the vertically polarized shear wave (dVsv) after 20 iterations based on comprehensive azimuth contrast tomography. The maximum peak-to-peak variation is 2.3%. The red and blue colors indicate the slow and fast shear wave velocities with respect to the average model generally associated with hot and cold materials, respectively. Credit: Ebru Bozdag, Colorado School of Mines

Earthquakes don’t just tangle roads and tear buildings down. Seismic waves from earthquakes pass through Earth, acting like giant MRI machines and providing clues about what’s inside the planet.

Seismologists have developed methods for taking wave signals from a network of seismometers on the Earth’s surface and reflecting the properties and characteristics of the medium through which they pass, a process known as seismic tomography.

for decades, tomography seismic It is based on the ray theory, and seismic waves are treated like light rays. This was a very good approximation and led to major discoveries about the Earth’s interior. But to improve the accuracy of current seismic tomographic models, seismologists need to consider the full complexity of wave propagation using numerical simulations, known as full-wave inversion, said Ebru Bozdag, professor in the Department of Geophysics at the Colorado College of Mines. .

“We’re at a point where we need to avoid approximations and corrections in our imaging techniques to build this model from the ground up,” he said.

Bozdag was the lead author of the first full wave reflection Model, GLAD-M15 in 2016, based on full 3D waveform simulation and sensitivity of 3D data on a global scale. The open source SPECFEM3D_GLOBE 3D model was used to solve global wave propagation and was created in collaboration with researchers from Princeton University, Marseille University, King Abdullah University of Science and Technology (KAUST) and Oak Ridge National Laboratory (ORNL). The work was praised in the media. Its successor, GLAD-M25 (Lei et al. 2020), appeared in 2020 and exhibits prominent features such as subduction zones, mantle plumes, and hotspots for further discussion of mantle dynamics.

“We demonstrated the feasibility of using full 3D waveform simulation and data sensitivity for seismic standards at a global level in our 2016 and 2020 papers. Now, it’s time to use better standards to describe the physics of Earth’s interior in reverse,” he said.

At the American Geophysical Union’s fall meeting in December 2021, Bozdag, postdoctoral researcher Ridvan rsvuran, Ph.D. Student Armando Espindola Carmona, computational seismologist Daniel Peter of KAUST, and collaborators presented the results of their efforts to model full global wave reflection attenuation—a measure of energy loss during seismic wave propagation within the Earth—and azimuth anisotropy—including the way the wave velocity varies as a function of direction. The propagation azimuth as well as the radial variance were taken into account in the first generation GLAD model.

They used data from 300 earthquakes to build a new global full-wave reflection model. “We update this Earth model so that the variation from the observed and simulated data is often reduced,” he said. “And we’re trying to understand how our models swap, elastic and inelastic, with each other, which is a difficult task.”

The research was supported by the National Science Foundation (NSF) CAREER Award, supported by the Frontera supercomputer at the Center for Advanced Computing in Texas – the fastest of any university and the 13th fastest in the world – and the Marconi100 system in Cineca, the largest computing hub. Italy.

“By accessing Frontera, publicly available data from around the world, and the power of our modeling tools, we are beginning to approach continent-level accuracy in global full-wave reflection models,” he said.

Bozdag hopes to provide a better definition of the origin of the mantle fur and the water content of the upper mantle. Furthermore, “to accurately pinpoint earthquake locations and other earthquake sources, identify earthquake mechanisms and better relate them to plate tectonics, you need to have high-resolution models of the crust and mantle,” he said.

From the depths of the sea to outer space

Marsquake— Cerberus Fossae Event (Mw 3.1). The visualization shows the seismic wave velocity (vertical component). The researchers used Frontera to simulate the event, in collaboration with the NASA InSight mission. Credit: Daniel Peter, KAUST

Bozdag’s work is not limited to land. He also shared his experience in numerical simulation With NASA’s InSight mission as part of the science team to design the interior of Mars.

Early details of the Martian crust are limited by seismic data For the first time published in to know September 2021. Bozdag, together with the InSight team, continues to analyze swamp data and finalize details of the planet’s interior from crust to core with the help of 3D wave simulations conducted on Frontera.

The Mars work takes into account the lack of data in some parts of the Earth, especially beneath the oceans. “We now have data from other planets, but it’s still difficult to get high-resolution images under the sea due to a lack of tools,” said Bozdag.

To address this, he integrates data from emerging instruments into his model as part of the NSF CAREER awards, such as those from the floating acoustic robot known as MERMAID (Oceanic Portable Seismic Recording by Autonomous Divers). These autonomous submarines can capture seismic activity at sea and rise to the surface to communicate that data to scientists.

Seismic community access

In September 2021, Bozdag was part of a $3.2 million NSF award-winning team to create a computing platform for the seismological community, known as SCOPED (Seismic Platform for Gap Detection), in collaboration with Carl Tape (University of Alaska-Fairbanks), Marine Dinnell (University of Washington), Felix Waldhauser (Columbia University), and Ian Wang (TACC).

“The SCOPED project will create a computing platform, powered by Frontera, that provides data, computing, and services to the seismological community to advance education, innovation, and discovery,” said Wang, the project’s research associate and principal investigator of the project. . “TACC will focus on developing critical electronic infrastructure serving data-driven computing and research, including seismic imaging, wave modeling, ambient noise seismology, and precision seismic monitoring.”

Another community-oriented project of the Bozdag group is the Ph.D. Student Caio Ciardelli recently launched SphGLLTools: a visualization toolkit for large seismic model files. The toolkit-based makes it easy to plan and share global CT models with the community. Description of team tools in Computer science and the earth In February 2022.

“We provide a full suite of computational tools to visualize our additional global model,” said Bozdag. “Anyone can take our models based on HPC simulations and convert them to a format to enable their visualization on a PC and use a collaborative laptop to understand each step.”

Robin Reichlin, Director of the Geophysics Program at NSF said, “With the new and improved full wave model; tools to reduce community data access and analysis; and a supercomputer-powered platform to allow seismologists to discover the mysteries of Earth and other depths. the inner planet, Bozdag pushes the field into more accurate and open territory.

further information:

Caio Ciardelli et al., SphGLLTools: Toolkit for visualizing large seismic model files based on 3D spectral element networks, Computer science and the earth (2021). DOI: 10.1016 / j.cageo.2021.105007

Brigitte Knappmayr-Andron et al., The thickness and structure of the Martian crust from Insight seismic data, to know (2021). DOI: 10.1126 / science.abf8966

Equipment: github.com/caiociardelli/sphglltools

quotePlanetary Magnetic Resonance Imaging: High Resolution Illumination of the Earth’s Inside to the Planet’s Core (2022, 29 March) Accessed March 29, 2022 from https://phys.org/news/2022-03-planet-scale-high-resolution mri-illumination . html

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