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Earthquake Connection

Years before the devastating Tohoku earthquake struck the coast of Japan in 2011, the Earth’s crust near the site of the quake was starting to stir. The proximity of the barely perceptible tremors raises a question: Could they have foreshadowed the big quake or even set it in motion?

This question is driving research into a computer model that is helping untangle the connection between the small shakes and the destruction that followed.

Researchers at The University of Texas at Austin are leading the work, which could help enhance scientists’ understanding of forces driving megathrust earthquakes — the world’s most powerful type of earthquake — and improve earthquake hazard assessment.

The study was published on Dec. 15, 2018, in Earth and Planetary Science Letters. Lead author Thorsten Becker, a professor at the UT Jackson School of Geosciences and a researcher at the University of Texas Institute for Geophysics, said the study was the first to show changes in tremor activity before the Tohoku megathrust earthquake.

“The part of the crust that is close to the place that eventually ruptured changes stress state a couple of years before the event,” said Becker. “By demonstrating this, our work complements studies of crustal deformation and our understanding of the forces driving earthquakes.”

While the location of the tremors raises questions about their potential linkage to the quake, Becker said that it’s unknown at the moment if the two events relate. However, the seismic signature of the tremors is helping refine a computer model that could help answer that question. This new modeling technique allows scientists to create a four-dimensional image of the Earth’s crust and interactions between tectonic plates, showing how forces pushing at the fault change over time. Becker believes that with the right research and support, advanced computer models can be used to study the physics of earthquakes and perhaps contribute to improved forecasts. Currently, scientists can at best offer hazard maps showing known earthquake zones and a vague probability of an earthquake in the coming decades.