A new method for the computation of global viscoelastic post-seismic deformation in a realistic earth model (II)-horizontal displacement   总被引：1，自引：0，他引：1  

Y. Tanaka  J. Okuno  S. Okubo 《Geophysical Journal International》2007,170(3):1031-1052

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Seismic Properties of Anita Bay Dunite: an Exploratory Study of the Influence of Water     

Aizawa  Yoshitaka; Barnhoorn  Auke; Faul  Ulrich H.; Fitz Gerald  John D.; Jackson  Ian; Kovacs  IstvAn 《Journal of Petrology》2008,49(4):841-855

As a pilot study of the role of water in the attenuation ofseismic waves in the Earth's upper mantle, we have performeda series of seismic-frequency torsional forced-oscillation experimentson a natural (Anita Bay) dunite containing accessory hydrousphases, at high temperatures to 1300°C and confining pressure(P_c) of 200 MPa, within a gas-medium high-pressure apparatus.Both oven-dried and pre-fired specimens wrapped in Ni–Fefoil within the (poorly) vented assembly were recovered essentiallydry after 50–100 h of annealing at 1300°C followedby slow staged cooling. The results for those specimens indicatebroadly similar absorption-band viscoelastic behaviour, butwith systematic differences in the frequency dependence of strain-energydissipation Q^–1, attributed to differences in the smallvolume fraction of silicate melt and its spatial distribution.In contrast, it has been demonstrated that a new assembly involvinga welded Pt capsule retains aqueous fluid during prolonged exposureto high temperatures—allowing the first high-temperaturetorsional forced-oscillation measurements under high aqueousfluid pore pressure P_f. At temperatures >1000°C, a markedreduction in shear modulus, without concomitant increase inQ^–1, is attributed to the widespread wetting of grainboundaries resulting from grain-scale hydrofracturing and themaintenance of conditions of low differential pressure P_d =P_c – P_f . Staged cooling from 1000°C is accompaniedby decreasing P_f and progressive restoration of significantlypositive differential pressure resulting in a microstructuralregime in which the fluid on grain boundaries is increasinglyrestricted to arrays of pores. The more pronounced viscoelasticbehaviour observed within this regime for the Pt-encapsulatedspecimen compared with the essentially dry specimens may reflectboth water-enhanced solid-state relaxation and the direct influenceof the fluid phase. The scenario of overpressurized fluids andhydrofracturing in the Pt-encapsulated dunite specimen may havesome relevance to the high Q^–1 and low-velocity zonesobserved in subduction-zone environments. The outcomes of thisexploratory study indicate that the presence of water can havea significant effect on the seismic wave attenuation in theupper mantle and provide the foundation for more detailed studieson the role of water. KEY WORDS: seismic wave attenuation; water; dunite; hydrous mineral; shear modulus; viscoelasticity; olivine; grain-scale hydrofracturing  相似文献   

Viscoelastic perturbations of the earth: significance of the incremental gravitational force in models of glacial isostasy     

Falk Amelung  Detlef Wolf 《Geophysical Journal International》1994,117(3):864-879

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Time-averaged and time-dependent energy-related quantities of harmonic waves in inhomogeneous viscoelastic anisotropic media     

Vlastislav &#;ervený  Ivan P&#;en&#;ík 《Geophysical Journal International》2007,170(3):1253-1261

The energy–flux vector and other energy-related quantities play an important role in various wave propagation problems. In acoustics and seismology, the main attention has been devoted to the time-averaged energy flux of time-harmonic wavefields propagating in non-dissipative, isotropic and anisotropic media. In this paper, we investigate the energy–flux vector and other energy-related quantities of wavefields propagating in inhomogeneous anisotropic viscoelastic media. These quantities satisfy energy-balance equations, which have, as we show, formally different forms for real-valued wavefields with arbitrary time dependence and for time-harmonic wavefields. In case of time-harmonic wavefields, we study both time-averaged and time-dependent constituents of the energy-related quantities. We show that the energy-balance equations for time-harmonic wavefields can be obtained in two different ways. First, using real-valued wavefields satisfying the real-valued equation of motion and stress–strain relation. Second, using complex-valued wavefields satisfying the complex-valued equation of motion and stress–strain relation. The former approach yields simple results only for particularly simple viscoelastic models, such as the Kelvin–Voigt model. The latter approach is considerably more general and can be applied to viscoelastic models of unrestricted anisotropy and viscoelasticity. Both approaches, when applied to the Kelvin–Voigt viscoelastic model, yield the same expressions for the time-averaged and time-dependent constituents of all energy-related quantities and the same energy-balance equations. This indicates that the approach based on complex-valued representation of the wavefield may be used for time harmonic waves quite universally. This study also shows importance of joint consideration of time-averaged and time-dependent constituents of the energy-related quantities in some applications.  相似文献   

Using the Post–Widder formula to compute the Earth's viscoelastic Love numbers     

G. Spada  L. Boschi 《Geophysical Journal International》2006,166(1):309-321

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Distributed Nubia–Somalia relative motion and dike intrusion in the Main Ethiopian Rift     

R. Bendick  S. McClusky  R. Bilham  L. Asfaw  S. Klemperer 《Geophysical Journal International》2006,165(1):303-310

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Stress transfer relations among the earthquakes that occurred in Kerman province, southern Iran since 1981   总被引：1，自引：0，他引：1  

Suleyman S. Nalbant  Sandy Steacy  John McCloskey 《Geophysical Journal International》2006,167(1):309-318

We explore the possible stress triggering relationship of the   M ≥ 6.4  earthquakes that occurred in Kerman Province, southern Iran since 1981. We calculated stress changes due to both coseismic sudden movement in the upper crust and the time-dependent viscous relaxation of the lower crust and/or upper mantle following the event. Four events of   M ≥ 6.4  occurred between 1981 and 2005, on and close to the Gowk fault, show a clear Coulomb stress load to failure relationship. The  2003 M = 6.5  Bam earthquake, however, which occurred approximately 95 km SW of the closest Gowk event, shows a very weak stress relation to preceding earthquakes. The coseismic static stress change at the hypocentre of the Bam earthquake is quite small (∼0.006 bars). The time-dependent post-seismic stress change could be 26 times larger or 7 times lower than that of coseismic static stress alone depending on the choice of viscoelastic crustal model and the effective coefficient of friction. Given the uncertainties in the viscoelastic earth models and the effective coefficient of friction, we cannot confidently conclude that the 2003 Bam event was brought closer to failure through coseismic or post-seismic stress loading. Interestingly, the southern Gowk segment with a similar strike to that of the Bam fault, experienced a stress load of up to 8.3 bars between 1981 and 2003, and is yet to have a damaging earthquake.  相似文献   

A computationally feasible approximate resolution matrix for seismic inverse problems     

Susan E. Minkoff 《Geophysical Journal International》1996,126(2):345-359

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Initial-value and modal approaches for transient viscoelastic responses with complex viscosity profiles     

Ladislav Hanyk  David A. Yuen  Ctirad Matyska 《Geophysical Journal International》1996,127(2):348-362

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Time domain analysis of generalized viscoelastic models     

Nicos Makris 《Soil Dynamics and Earthquake Engineering》1995,14(5)

This paper examines the convolution integral method for the time domain analysis of viscoelastic models with complex parameters. Such models have been extensively used in soil dynamics and base isolation studies, because they can predict realistically the non-viscous behavior of practical materials such as soil, acrylic polymers, and silicone gels among others. Starting from the constant hysteretic model which was initially proposed to model the behavior of dry sands, it is shown that the basic response functions of complex-parameter viscoelastic models are complex valued functions. The classical relations between the basic response function and the dynamic modulus are extended for the case of these generalized viscoelastic models. Finally, the time domain response of practical constitutive models with complex parameters is investigated, and the limitations and advantages of the convolution integral method are discussed.  相似文献