Schardong, L; Chevrot, S; Garcia, RF; (2013) Global P- and S-wave tomography from finite-frequency traveltime residual measurements. Presented at: American Geophysical Union Fall Meeting, San Francisco, USA.

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Abstract

There are two main ways to improve the resolution of tomographic images: building larger and higher quality datasets, and using better imaging theories, such as finite frequency theory or waveform inversion, instead of the more commonly used ray theory. A first step toward improving the resolution of global tomographic models is thus to construct a seismological database adapted to finite-frequency tomography or waveform inversion. We present a global dataset of finite frequency travel time residuals. These measurements were obtained by cross-correlating observed and synthetic waveforms in several frequency bands. We exploit seismograms at significantly shorter periods than in other recent comparable works. We compute Green's functions with the GEMINI method and convolve them with high-frequency source-time functions. These source-time functions are inverted, along with focal depths, with a simulated annealing approach. We measure travel time residuals on different P and S phases. We check the quality of our global database by performing preliminary tomographic inversions using ray theory. We use the subset of measurements performed in the 0.0725-Hz frequency range, combined to ISC travel times, to build tomographic models for both P and S velocity anomalies. Resulting models are presented and compared to recently published global tomographic models, and some implications for finite frequency effects and physical properties of the deep Earth are discussed.

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