Equations of state of close-packed phases of iron and their implications for the Earth's core     

F. Mulargia  E. Boschi 《Physics of the Earth and Planetary Interiors》1979,18(1):13-19

Theoretical equations of state for Fe at high pressures and temperatures are derived from the expression of the free energy written as a sum of the static energy, the harmonic, the anharmonic and the electronic contributions. All the calculations have been performed for the various crystal structures of Fe using different intermolecular potentials, and namely: Lennard-Jones, Morse and Rydberg functions. The available experimental data do not allow a definite choice between them thus leaving open the problem of the composition of the earth's core.  相似文献   

Body force,body couple and heat source equivalents for seismic dislocations     

Enzo Boschi 《Pure and Applied Geophysics》1973,111(1):2147-2157

Summary An explicit expression is derived for the body force, body couple and heat source to be applied in the absence of a seismic dislocation, which produces a thermodynamical behaviour equivalent to that produced by the dislocation.  相似文献   

Quasi-static crack models and the frictional stress threshold criterion for slip arrest     

M. Bonafede  M. Dragoni  E. Boschi 《Geophysical Journal International》1985,83(3):615-635

Summary. Two-dimensional crack problems in elastic homogeneous isotropic media are considered which describe rupture over a fault surface characterized by non-uniform stress drop. Solutions can be found in which the stress field is finite at the crack tips and the rupture surface is not assigned a priori , but is part of the solution. These crack models are found to be consistent with the frictional stress threshold criterion for slip arrest over pre-existing fault surfaces. A crack is found to stop when its contribution to the stress field is opposite to the stress drop at the crack tips. The quasi-static propagation of a crack up to the arrest configuration is studied in terms of the minimum energy principle. The crack spontaneously propagates in such a way as to make the value of the stress intensity factor at one tip equal to the value at the other tip. Furthermore a tip propagating in a region with higher friction is found to move more slowly than the other tip propagating in a region with lower friction. Simple criteria for fracture arrest are derived, in terms of a properly averaged stress drop. Piecewise constant stress drop profiles are explicitly considered yielding a variety of solutions which can be applied to modelling asperities or barriers over a fault plane. The evaluation of the amount of the energy released during the quasi-static crack propagation shows that stopping phases cannot be efficiently radiated if the crack comes to rest in a low friction region.  相似文献   

Multiple resolution surface wave tomography: the Mediterranean basin     

L. Boschi  G. Ekström  B. Kustowski 《Geophysical Journal International》2004,157(1):293-304

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Seismic deformation in the Mediterranean area estimated by moment tensor summation   总被引：2，自引：0，他引：2  

S. Pondrelli  A. Morelli  E. Boschi 《Geophysical Journal International》1995,122(3):938-952

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Heat diffusion and size reduction of a spherical magma chamber     

M. Bonafede  M. Dragoni  E. Boschi 《Bulletin of Volcanology》1984,47(2):343-347

An analytical solution is derived for the size reduction of a spherical magma chamber cooling by conduction. The use of moving boundary conditions and the constraint of a spherical symmetry allow one to ignore the details of the heat redistribution processes which take place within the magma chamber. The dependence of the solution on the initial conditions is investigated. A simple solution is found for short time, which is shown to be valid for times long enough to make it useful in the volcanological context. Moreover, the general solution confirms that the hydrothermal contribution to heat transfer in Phlegraean Fields cannot be extremely important.  相似文献   

The dynamical equations of polar wander and the global characteristics of the lithosphere as extracted from rotational data     

David A. Yuen  Roberto Sabadini  Enzo Boschi 《Physics of the Earth and Planetary Interiors》1983,33(3):226-242

The initial value problem describing the linear responses of the spin axis of a layered viscoelastic planet from surface loading is studied by means of Laplace transform techniques. A complete solution of polar motion requires the usage of two classes of eigenspectra: one arising from viscoelastic relaxation of the mantle due to surface forcing, the other involving the gradual readjustment of the spin axis as a consequence of mantle viscoelasticity. Our analytical 4-layer model comprising an elastic lithosphere, a two-layer, adiabatically stratified, viscoelastic mantle and an inviscid core has been incorporated into this formalism in which rotational deformation and isostatic relaxation are taken into account for all times. From employing both sets of rotational data, polar variations from the 70 years of data from the International Latitude Service (I.L.S.) and the non-tidal deceleration of the length of the day (l.o.d.) an estimate of the globally averaged lithosphere of between 130 and 200 km is obtained from the long wavelength flexural mode due to the degree-two harmonic. This range of values may have strong implications on the mode of continental evolution.  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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Fault slip beyond a barrier on a transform plate boundary     

M. Bonafede  E. Boschi  M. Dragoni 《Geophysical Journal International》1983,75(1):143-153

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Magnetic features of the magmatic intrusion that occurred in the 2007 eruption at Stromboli Island (Italy)     

Rosalba Napoli  Gilda Currenti  Ciro Del Negro  Agnese Di Stefano  Filippo Greco  Enzo Boschi 《Bulletin of Volcanology》2011,73(9):1311-1322

Significant changes in the local magnetic field marked the resumption of eruptive activity at Stromboli volcano on February 27, 2007. After differential magnetic fields were obtained by filtering out external noise using adaptive filters and seasonal thermal noise using temperature data, we identified step-like changes of 1–4 nT coincident with the opening of eruptive fissures in the upper part of the Sciara del Fuoco. The magnetic variations detected at two stations are closely related to the propagation of a shallow NE–SW magmatic intrusion extending beyond the summit craters area. These observations are consistent with those calculated using piezomagnetic models in which stress-induced changes in rock magnetization are produced by the magmatic intrusion. No significant magnetic changes were observed when the first fractures opened along the NE crater rim. Indeed, the stress-induced magnetization caused by this magmatic activity is expected to be too low because of the structural weakness and/or thermal state of the summit area. The continuous long-term decay characterizing the post-eruptive magnetic pattern can be related to a time-dependent relaxation process. A Maxwell rheology was assumed and the temporal evolution of the piezomagnetic field was evaluated. This allowed us to estimate the rheological properties of the medium; in particular, an average viscosity ranging between 10¹⁶ and 10¹⁷ Pa⋅s was a relaxation time τ of about 38 days.  相似文献