The SPiRaL global-scale seismic tomography model and full-waveform predictions from this non-full-waveform image of the crust and mantle

Abstract:

SPiRaL is a global-scale joint image of shear and compressional wave speeds based on millions of P- and S-wave travel time arrivals as well as global surface wave dispersion estimates for Rayleigh and Love waves. The model consists of more than 2.1 million model nodes, with 5 free parameters at each node to account for transverse anisotropy for P-, Sh-, and Sv-waves at any arbitrary direction of travel. We employ our custom multi-resolution approach (Simmons et al. 2011) that exploits spherical tessellation grids and hierarchies with the highest attempted resolution scale of ~0.25 degrees in portions of the crust and upper mantle in well-sampled regions throughout North America and Eurasia. While it is known that the relatively high-resolution global SPiRaL model predicts travel times (including surface wave travel times) since those data drive the model, the ability of the model to predict full-waveforms is untested. By computing full waveforms for key events and comparing to predictions based on existing full-waveform models, we explore the efficacy of the SPiRaL model to produce comparative waveform predictions and the potential for SPiRaL to serve as a high-resolution starting model for global full-waveform inversion. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Security, LLC, Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-812493