Resolution and Covariance of the LLNL-G3D-JPS Global Seismic Tomography Model

Session: Advances in Seismic Imaging of Earth’s Mantle and Core and Implications for Convective Processes
Type: Oral
Date: 4/29/2020
Time: 11:45 AM
Room: 120 + 130
Description: 

Resolution and covariance of global seismic tomography models are most often unknown quantities. However, there are many potential applications of these matrices including tomographic filtering of geodynamic convection models where thermal and compositional hypotheses have been employed. In this study, we construct both the resolution and covariance matrices for the recent LLNL-G3D-JPS global joint model of P- and S-wave velocity (Simmons et al. 2015). The global tomography model consists of >1 million free parameters, creating matrices with >1 trillion elements. Given the scale of the problem and computational limitations, we employed a custom method to calculated impulse responses at every node in the Earth model and produced sparse, yet representative, resolution and covariance matrices that can be practically employed for several real applications. We demonstrate applications of the matrices to real problems, including path-specific travel time uncertainty estimates and tomographic filtering of geodynamic renditions of Earth structure. Importantly, the global tomography resolution filter will allow for more reasonable reconstructions of past mantle flow through an adjoint convection simulation process whereby various assumptions including the thermal and compositional properties of the mantle may be tested.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DEAC52-07NA27344.

Presenting Author: Nathan A. Simmons

Authors