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The concept of a relaxation spectrum is used to compute the absorption and dispersion of a linear anelastic solid. The Boltzmann aftereffect equation is solved for a solid having a linear relationship between stress and strain and their first time derivatives, the 'standard linear solid', and having a distribution of relaxation times. The distribution function is chosen to give a nearly constant Q over the seismic frequency range. Both discrete and continuous relaxation spectra are considered. The resulting linear solid has a broad absorption band which can be interpreted in terms of a superposition of absorption peaks of individual relaxation mechanisms.The accompanying phase and group velocity dispersion imply that one cannot directly compare body wave, surface wave, and free oscillation data or laboratory and seismic data without correcting for absorption. The necessary formalism for making these corrections is given. In the constant Q regions the correction is the same as that implied in the theories of Futterman, Lomnitz, Strick and Kolsky.

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Comparison of seismic velocities in mantle minerals, under mantle conditions, with seismic data is a first step toward constraining mantle chemistry. The calculation, however, is uncertain due to lack of data on certain physical properties. "Global" systematics have not proved very useful in estimating these properties, particularly for the shear parameters. A new approach to elasticity estimation is used in this study to produce estimates of unknown quantities, primarily pressure and temperature derivatives of elastic moduli, from the structural and chemical trends evident in the large amount of elasticity data now available. These trends suggest that the derivatives of unmeasured high-pressure phases can be estimated from "analogous" low-pressure phases. Using these predictions and the best available measurements, seismic velocities are computed along high-temperature adiabats for a set of mantle minerals using third-order finite strain theory. The calculation of density and moduli at high temperature, to initiate the adiabat, must be done with care since parameters such as thermal expansion are not independent of temperature. Both compressional and shear seismic profiles are well-matched by a mineralogy dominated by clinopyroxene and garnet and with an olivine content of approximately 40% by volume. Between 670 and 1000 km, perovskite alone provides a good fit to the seismic velocities. Combining seismic velocities with recent phase equilibria data for a hypothetical pure olivine mantle suggests that a mineralogy with a maximum of 35% olivine (shear profile) or 40-53% olivine (compressional profile) by volume can satisfy the constraint imposed by the 400-km discontinuity. Other features of the upper mantle can then be matched by appropriate combinations of pyroxenes, garnets, and their high-pressure equivalents. While mantle models with a substantially larger fraction of olivine cannot be ruled out, they are acceptable only if the derivatives of the spine! phases are substantially different from olivine and deviate from trends in the larger data set.

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Theory of the Earth is an interdisciplinary advanced textbook on the origin, composition, and evolution of the Earth's interior: geophysics, geochemistry, dynamics, convection, mineralogy, volcanism, energetics and thermal history. This is the only book on the whole landscape of deep Earth processes which ties together all the strands of the subdisciplines. It is a complete update of Anderson's Theory of the Earth (1989). It includes many new sections and dozens of new figures and tables. As with the original book, this new edition will prove to be a stimulating textbook on advanced courses in geophysics, geochemistry, and planetary science, and supplementary textbook on a wide range of other advanced Earth science courses. It will also be an essential reference and resource for all researchers in the solid Earth sciences.

Much of the Pacific rim appears to be accreted terrain which originated in the Pacific," The possibility of a continent centrally located in the pacific, Pacifica, has been discussed for some time, g but its location has been an enigma and its size uncertain. In Japan, 9 both of which formed in equational latitudes and subsequently drifted to the north and northwest respectively. They may record the initial rift stages_ of continental crusts We speculate that they also farmed in the Pacific geoid high.We propose that episodicity in continental drift, polar wander, sea-level variations and magmatism is due to the effect of thick continental lithosphere on convection in the mantle. My, then we might expect that these features will wane with time.Horizontal temperature gradients can drive continental drift. 2021,22s23 ,2 9. The velocities decrease as the distance increases away from the heat source and as the thermal anomaly decays due to Pangea during the early Mesozoic, the mantle will warm up and/or partially melt. In either case a geoid anomaly will develop. This anomaly will affect convection and plate motions in a manner previously suggested2 0923 and will also affect the rotation axis of the Earth.25Since the thermal anomalies appear to be long-lived and it takes a long time to establish a new thermal regime, major shifts of the rotation axis due to this mechanism will be infrec-uent and gradual.

The source parameters of the 1994 Bolivian earthquake (magnitude Mw = 8.3) suggest that the maximum seismic efficiency eta was 0.036 and the minimum frictional stress was 550 bars. Thus, the source process was dissipative, which is consistent with the observed slow rupture speed, only 20% of the local S-wave velocity. The amount of nonradiated energy produced during the Bolivian rupture was comparable to, or larger than, the thermal energy of the 1980 Mount St. Helens eruption and was sufficient to have melted a layer as thick as 31 centimeters. Once rupture was initiated, melting could occur, which reduces friction and promotes fault slip.