HR: 1330h
AN: T32B-0926 [PDF]
TI: Combined Constraints From Seismic and Mineral Physics Data on the 1D Velocity Structure of the Mantle:
Towards a Physical Reference Model
AU: * Cammarano, F
EM: fabio@tomo.ig.erdw.ethz.ch
AF: Institut fur Geophysik, ETH, Zurich, 8093
Switzerland
AU: Goes, S
EM:
AF: Institut fur Geophysik, ETH, Zurich, 8093
Switzerland
AU: Deuss, A
EM:
AF: Department of Earth Sciences, University of Oxford, Oxford, OX1 3PR
United Kingdom
AU: Giardini, D
EM:
AF: Institut fur Geophysik, ETH, Zurich, 8093
Switzerland
AB:
The knowledge of thermal and compositional structure of the mantle is fundamental to understand many aspects of Earth
dynamics. Seismic tomography provides an uncomparable tool to explore the Earth's deep structure. But, seismic velocity
models obtained from inverting seismic data are not unique solutions. This is also the case for spherical reference models
that constitute the background model for most velocity structures in one, two and three dimensions. In particular, upper
mantle structure in both PREM and AK135, the most used 1-D Earth models, is not strongly constrained by the data used to
define these models. In this study, we combine mineral physics and seismic data (travel-times from the re-processed ISC
catalog of Engdahl et al., 1998 and the most recent normal mode frequency measurements to define a physical reference model
for the Earth's mantle. For the construction of this reference model, a pyrolitic composition and thermal structure for 60 My
old oceanic lithosphere and a mantle adiabat with a potential temperature of 1300$\deg$C are assumed. Within the range of
uncertainties of elastic and anelastic parameters from our recent compilation (Cammarano et al. 2003), we find a family of
models that provide a fit to both normal mode frequencies (surface waves frequency range included) and travel-times (P- and
S-phases) that is similar to PREM and AK135. The best-fit models can be used as reference model for tomographic inversions,
where the family of models allows for uncertainty evaluation. The advantages of using a physical reference model are that:
(1) anomalies relative to it represent deviations from an adiabatic pyrolite mantle, rather than from an average velocity;
(2) the chosen physical model is based on a set of mineral parameters which can also be used to for interpretation of
velocity structure in terms of temperature and compositional variations.
DE: 3909 Elasticity and anelasticity
DE: 7260 Theory and modeling
DE: 8124 Earth's interior--composition and state (old 8105)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting