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RSTT computes seismic travel times from its earth models in milliseconds, capturing the major effects of 3-D structure in the crust and upper mantle.
RSTT computes seismic travel times from its earth models in milliseconds, capturing the major effects of 3-D structure in the crust and upper mantle.

A three-lab NNSA team recently made a major upgrade to the software for understanding and utilizing the structure of Earth’s crust and upper mantle, which may allow researchers to better locate nuclear detonations. The model could more accurately geolocate clandestine underground nuclear tests by measuring how long it takes seismic waves to travel from one point on the globe to another.

If you have a more accurate seismic event location, you can use the other tools in your toolbox to determine whether or not a suspicious event was a clandestine nuclear test.

Dr. Brent Park
NNSA Deputy Administrator for Defense Nuclear Nonproliferation

The team, from Los Alamos National Laboratory, Lawrence Livermore National Laboratory, and Sandia National Laboratories, recently delivered a revision of the Regional Seismic Travel Time (RSTT) monitoring technology to a division of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) in Vienna.

The improved software was the result of years of development and includes almost a decade’s worth of new data on the geophysical model of Earth’s crust and upper mantle. The data set now includes information spanning all seven continents and ocean floor areas where earthquakes and other seismic events occur, providing more detail and improving the confidence in locations the system identifies.

“This is a great example of U.S. technical leadership helping the world,” said Dr. Brent Park, NNSA Deputy Administrator for Defense Nuclear Nonproliferation. “If you have a more accurate seismic event location, you can use the other tools in your toolbox to determine whether or not a suspicious event was a clandestine nuclear test.”

One such tool that can help confirm nuclear blasts is detecting radioactive noble gases, which are created during nuclear explosions and are difficult to hide. By providing a high-confidence seismic source location, RSTT helps the world’s noble gas detection experts focus their efforts on a specific area, enhancing accuracy.

RSTT was originally developed by the National Laboratories in the late 2000s, and they have helped hone the model and software ever since. Because of its utility in nuclear explosion monitoring, the U.S. government shared it with the CTBTO in 2012, where it has become a mainstay of the organization’s operations.

RSTT is publicly available for download at https://www.sandia.gov/rstt/.

RSTT uses the GeoTess software library to break the Earth down into approximately 1° triangles – tessellation – then calculates the speed of seismic waves through each.
RSTT uses the GeoTess software library to break the Earth down into approximately 1° triangles – tessellation – then calculates the speed of seismic waves through each.