Showing papers in "Physics of the Earth and Planetary Interiors in 1993"

TL;DR: In this article, the 3D P-wave velocity structure of the mantle below Europe, the Mediterranean region and a part of Asia Minor is investigated using the International Seismological Centre (ISC) data.

TL;DR: In this paper, the seismic properties of five South African kimberlite nodules have been calculated from petrofabric measurements, and the average of the five samples has a maximum S-wave anisotropy ( δV s ) of 3.7% which is sufficiently high to explain previously reported teleseismic SKS delay times in continental shield areas of up to 1.7 s.

TL;DR: In this paper, UFL electromagnetic emissions from the Spitak (Armenia) earthquake site have been detected at the Dusheti and Vardzia (Georgia) observatories in a frequency range 0.005-1 Hz.

TL;DR: In this article, the authors examined shear-wave splitting in teleseismic shear waves (SKS, SKKS, S) from 15 stations in the western United States, based on analysis of 123 records from 67 events.

TL;DR: In this article, the seismic properties of the crust have been modelled using hypothetical polycrystals with typical crustal compositions and commonly measured petrofabrics, which allows us to better evaluate and quantify the crustal contribution to splitting of teleseismic SKS-waves.

TL;DR: In this article, the crystal structure of NaMgF3 perovskite (Neighborite) has been studied at high temperature by X-ray powder diffraction using a position sensitive detector with a monochromatic synchroton radiation source.

TL;DR: Lower crustal xenoliths in alkaline volcanics of Europe have revealed that a wide range of rock types exist in the lower crust. as discussed by the authors showed that the mafic lower crust has been added to the base of the pre-existing crust by processes of intrusion and underplating, such additions to the crust have probably occurred during periods of subduction, rifting and orogenic collapse.

TL;DR: In this article, the effects of both depth-dependent thermal expansivity and depthdependent viscosity on mantle convection have been examined with two-dimensional finite-element simulations in aspect-ratio ten boxes.

TL;DR: In this paper, the relationship between low-field magnetic anisotropy and strain was investigated in the line/plane model and in the viscous model, and it was shown that the natural logarithm of the degree of anisotropic magnetic susceptibility to natural strain relationship can be approximately represented by a straight line, at least for low to intermediate strains.

TL;DR: A review of the high-frequency seismo-electromagnetic phenomena already observed, and occurring before, as well as after, the great Alaskan earthquake in 1964 can be found in this paper.

TL;DR: In this article, anisotropy formed either by hexagonal or by orthorhombic aggregates composed of olivine, orthopyroxene, and clinopyroxenes was found to fit combinations of both P and S seismological observations.

TL;DR: In this paper, an attempt is made to review the data and the proposed structural models with the aim of separating the certain from the probable and from the speculative information, which can be achieved by first reviewing the theoretical resolving power and ambiguity of the applied interpretation methods and then analysing the proposed models.

TL;DR: In this article, the seismic properties and their directional dependence have been measured in three potentially mantle-derived rocks (peridotite, Ivrea zone, Italy; lherzolitic xenolith, Massif Central, France; serpentinite).

TL;DR: In this article, the structural phase transition in NaMgF 3 perovskite can be modelled as a tricritical ferroelastic phase transition, and the coupling between the spontaneous strain and the octahedral tilts is in a linear-quadratic form.

TL;DR: In this paper, high-resolution seismic sounding of the mantle using two Peaceful Nuclear Explosions (PNEs) along the 3950 km long Quartz profile in northern Eurasia reveal major unexpected vertical and lateral mantle inhomogeneities.

TL;DR: The separable solutions of the fully nonlinear, convective dynamo with spherically symmetric buoyancy forces and boundary conditions arise from the group of symmetry operations that leave a rotating sphere unchanged; they are more general than the rather specialised solutions usually quoted in the geomagnetic literature as discussed by the authors.

TL;DR: Magnetotelluric measurements show the lower continental crust to be electrically conductive globally, typically 100-1000 times more conductive than dry rocks measured in the laboratory and 10-100 times higher conductivity than the middle to upper crust as mentioned in this paper.

TL;DR: In this article, the authors carried out measurements of compressional and shear-wave velocities up to 600 MPa confining pressure on amphibolite to granulite facies metapelites from the Serie dei Laghi and Ivrea-Verbano zone, northern Italy.

TL;DR: In this paper, the authors investigated the rotational motions of a simple Earth model composed of three homogeneous layers: an elastic inner core, a liquid outer core and an elastic mantle.

TL;DR: A cleaning strategy involves one or more cleaning methods applied in a specific sequence as discussed by the authors, which is made easier with a priori knowledge of magnetic mineralogy and granulometry, or in other words, rock magnetic properties.

TL;DR: The splitting of SKS-waves shows that the fast velocity is commonly parallel to the trend of mountain belts as discussed by the authors, which is related to the anisotropy induced by frozen mantle flow at lithospheric depth when the flow direction is parallel to mountain belts.

TL;DR: Hollerbach, R. and Jones, C. as mentioned in this paper presented a direct spectral solution for the mean-field geodynamo equations, with inertia neglected but viscosity retained, in a spherical shell.

TL;DR: The heat flow pattern of Europe, derived from more than 8000 observations, is dominated by a general northeast to southwest increase in geothermal activity, which is the consequence of the tectonic evolution of the whole continent as discussed by the authors.

TL;DR: In this article, a power-law creep behavior with a stress exponent of 35 ± 1 in both orientations has been observed: creep along the 〈110 ǫ orientation is much easier than creep along Ãǫǫ Þ orientation, while the dependence on oxygen fugacity is also different between the two orientations.

TL;DR: In this paper, a new integrated rock magnetic method of sample selection or rejection is proposed, which uses the combined results from "thermal" (thermomagnetic and high-temperature susceptibility) and "non-thermal'' (low-tem temperature susceptibility, hysteresis and alternating field demagnetisation) rock magnetic techniques to define sets of rock magnetic behaviour for Precambrian basalts, with a mixed grain size of pure magnetite.

TL;DR: In this paper, the authors presented the first attempt to use anisotropy of magnetic susceptibility (AMS) analysis for the characterization of the magnetic fabric of Plio-Pleistocene sediments in the southern Apennines of Italy.

TL;DR: In this paper, 20 magnetotelluric (MT) soundings in the Coast belt of southwestern British Columbia, Canada, in the vicinity of volcanic Mounts Meager and Cayley (approximately 150 km north of Vancouver), are analyzed to determine both the internal electrical conductivity structure of the Garibaldi volcanic belt and the regional conductivity structures.

TL;DR: In this paper, a dataset consisting of long-period waveforms (5-20 s) and differential travel times of S, ScS, and the arrival from the D″ layer, Scd, was used to investigate the laterally varying shear wave velocity (V S ) discontinuity at the base of the mantle.

TL;DR: In this paper, the non-double couple components in source moment tensors of intermediate-depth and deep earthquakes are significant and appear to respond to the state of predominant strain release within slabs, which is partially or fully induced by the sources themselves or by slab structures near the sources.

TL;DR: In this article, the authors used a transmission electron microscope (TEM) to clarify the dislocation characteristics of silicate garnets and found that dislocation densities of all the garnet-peridotites (ρ = 105−107 cm−2) are always nearly an order of magnitude lower than those of coexisting olivines.