### Abstract

The complete set of elastic stiffness coefficients of a single crystal of Mg_{2}SiO_{4} in the modified spinel (wadsleyite) structure are reported at eight pressures from ambient to 14 Gigapascals (GPa). All moduli vary linearly with pressure within the resolution of the data. Third-order Birch-Murnaghan equation fits to aggregate elastic moduli yield values of 170 (± 2) GPa and 4.3 (± 0.2) for the adiabatic bulk modulus and its first pressure derivative, and 115 (± 2) GPa and 1.4 (± 0.2) for the shear modulus and its first pressure derivative. These data, together with previous results for α-Mg_{2}SiO_{4}, enable us to make the first in situ determination of the velocity increase due to the α-β transition at the pressure (∼ 13.8 GPa) of the 410 km discontinuity. The room-temperature velocity increase at the transition pressure is 9.8% for compressional waves and 12.4% for shear waves.

Original language | English (US) |
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Pages (from-to) | E9-E15 |

Journal | Earth and Planetary Science Letters |

Volume | 147 |

Issue number | 1-4 |

State | Published - Mar 1 1997 |

### Keywords

- Elasticity
- Spinel
- Transition zones
- Upper mantle

### ASJC Scopus subject areas

- Geophysics
- Geochemistry and Petrology
- Earth and Planetary Sciences (miscellaneous)
- Space and Planetary Science

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## Cite this

_{2}SiO

_{4}to the pressure of the 410 km seismic discontinuity in the Earth's mantle.

*Earth and Planetary Science Letters*,

*147*(1-4), E9-E15.