2009 Fall AGU Abstract

Lou, X., S. Jacobsen, S. van der Lee, C. Bina, and Y.-Y. Chang, Modeling effects of hydration on mantle elasticity: A comparison with seismology, Program and Abstracts of the 2010 Annual Meeting of COMPRES, 31, 2010.

Seismological observations can provide constraints on velocity and density structures in the Earth's interior and yield various global-average models (such as PREM, IASP91 and AK135) and regional models (such as TNA, SNA and NA04). Velocity anomalies in regional models with respect to reference global models can be caused by variations in temperature and composition. Particularly, water content is an important factor because it can be incorporated (up to several weight percent) in the structures of the major mantle minerals olivine, wadsleyite and ringwoodite in the form of hydroxyl (OH)-. Hydration influences seismic velocities of the (Mg,Fe)2SiO4 polymorphs by reducing the elastic moduli and changing the pressure and temperature derivatives of the moduli. To study the effects of hydration on seismic velocities in detail, we perform finite-strain forward modeling of velocities using a compilation of recent mineral physics laboratory data. P- and S-wave velocity profiles are calculated from density, elastic moduli, pressure and temperature derivatives of moduli and thermal expansion coefficients of mantle rock-forming minerals. In the calculations, water content is a variable in the depth profile which can be derived from studies of water solubility and water partitioning coefficients for olivine, wadsleyite and ringwoodite. Therefore, velocity models from both mineral physics and seismology can be compared and help to interpret the velocity variations in seismic models.

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