Global Analyses of Body Wave Travel Times and Amplitudes: Whole-Mantle Tomography and Simulations of 3-D Wave Propagation

California Institute Of Technology, Pasadena CA

Investigators

Abstract

Abstract for proposal EAR0106666 (PH # 53x) Title: Global Analyses of Body Wave Travel Times and Amplitudes: Whole-mantle Tomography and Simulations of 3-D Wave Propagation PI's: Jeroen Tromp and Jeroen E. Ritsema, Cal Tech Seismic tomographic models are beneficial to researchers from a wide variety of disciplines in the Earth Sciences. They provide images of the structure of oceanic and continental lithosphere, and play a central role in constraining the planform of convection in the mantle. To improve these models, we will construct new tomographic models in which we will take advantage of the extensive seismic data set that we have compiled in the past several years. It includes unique data types, such as higher-mode Rayleigh wave phase-velocity measurements and travel times of converted body-wave phases (e.g., SP, SKP), which have not been fully exploited in tomography. In a parallel research effort, we apply the new Spectral Element Method of Komatitsch and Tromp [1999] to study the effects of 3-D mantle structure on long-period body-wave propagation. Specifically, we will test the applicability of ray theory to wave propagation in `low-degree' seismic models, whether small-scale structure in the deep mantle, such as plumes, produce characteristic, observable travel-time or waveform variations, and whether the large-scale pattern of long-period body-wave amplitude anomalies can be explained by large-scale variation of seismic velocity in the mantle. These analyses provide insight into the quality of present-day tomographic models and help us design the next generation of tomographic inversions when fully 3-D forward theories can be incorporated.