Under the sponsorship of the National Nuclear Security Administration’s Office of Defense Nuclear Nonproliferation R&D, Sandia National Laboratories and Los Alamos National have partnered to develop a 3D model of the Earth’s mantle and crust called SALSA3D, or Sandia-Los Alamos 3D. The purpose of this model is to assist in more accurately locating all types of explosions.

The model uses a scalable triangular tessellation and seismic tomography to map the Earth’s “compressional wave seismic velocity,” a property of the rocks and other materials inside the Earth that indicates how quickly compressional waves travel through them and is one way to accurately locate seismic events. Compressional waves — measured first after seismic events — move the particles in rocks and other materials minute distances backward and forward between the location of the event and the station detecting it.

SALSA3D also reduces the uncertainty in the model’s predictions, an important feature for decision-makers who must take action when suspicious activity is detected. In recent tests, SALSA3D was able to predict the source of seismic events over a geographical area that was 26 percent smaller than the traditional one-dimensional model and 9 percent smaller than a recently developed Regional Seismic Travel Time (RSTT) model used with the one-dimensional model.

Sandia recently released SALSA3D’s framework — the triangular tessellated grid on which the model is built — to other Earth scientists, seismologists and the public. By standardizing the framework, the seismological research community can more easily share models of the Earth’s structure and global monitoring agencies can better test different models.