A study of long-period mantle wave scattering
Abstract
This study examines long-period mantle wave scattering on the global scale. To this end, we extend a set of existing long wavelength global tomographic shear-velocity models with a random von-Karman model to add heterogeneities at much smaller scales. The spectrum of the random model is chosen to match the power of regional models at small scales and to transfer smoothly to the global model at long scales. Because such a model includes heterogeneities with realistic strengths at scales equal and smaller than wavelengths of long-period mantle signals (> 100s) we can examine the strong scattering regime. We use a spherical-harmonics multitaper approach to estimate the power spectrum of different regional models. We compare them to the power spectrum of global models estimated from the same region, and show that both spectra transfer reasonably smoothly into each other. The heterogeneity spectrum can be approximated by a von-Karman spectrum which is a decreasing power-law at short scales. We extend the global models in the upper mantle, based on these estimates of the short scale power spectra, and in the lower mantle, by extrapolation. Naturally, knowledge of the power spectrum alone, limits our models to realistic two-point correlations on short scales, neglecting higher orders. The consequences of such semi-statistical high-resolution models on the spectro-temporal behavior of long-period waveforms are analyzed using long time (> 30h) global spectral element simulations. We focus on measuring the scattering attenuation and the behavior of the envelopes to compare with real data and better constrain the spectral character of earth models at short wavelengths.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMDI41A2320M
- Keywords:
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- 7208 SEISMOLOGY Mantle;
- 7290 SEISMOLOGY Computational seismology;
- 7255 SEISMOLOGY Surface waves and free oscillations