The nature of the Moho in Australia from reflection profiling: A review

AbstractThe transition between the crust and mantle across the Australian continent shows considerable variations in both depth and sharpness. Recent extensive seismic reflection profiling provides a comprehensive data set to investigate the nature of the Moho in a wide range of geological environments. In reflection seismology the crust is normally characterized by distinct reflectivity whose base is taken as the location of the reflection Moho. This attribution to the base of the crust ties well to refraction and receiver function studies that make a more direct estimate of the depth to the base of the crust. The character of the reflection Moho varies widely across the Precambrian areas of Australia with no consistent link to the surface geology or the estimated age of the crust. In a number of places a double Moho is preserved with underthrusting, suggesting that the reflection Moho is a very ancient feature (at least 1400Ma in the Capricorn Orogen). Elsewhere, the current Moho reflects multiple generations of crustal reworking

Семантична еволюція латинських і романських дієслів із значенням «звертатися»

Статья из специализированного выпуска научного журнала "Культура народов Причерноморья", материалы которого объединены общей темой "Язык и Мир" и посвящены общим вопросам Языкознания и приурочены к 80-летию со дня рождения Николая Александровича Рудякова.Стаття із спеціалізованого випуску наукового журналу "Культура народов Причерноморья", матеріали якого поєднані загальною темою "Мова і Світ" і присвячені загальним питанням мовознавства і приурочені до 80-річчя з дня народження Миколи Олександровича Рудякова

CP violating neutrino oscillation and uncertainties in Earth matter density

We propose a statistical formulation to estimate possible errors in long baseline neutrino oscillation experiments caused by uncertainties in the Earth matter density. A quantitative investigation of the effect is made on the CP asymmetry in future neutrino factory experiments.Comment: Latex, 10 pages, 5 figure

Multimode surface wave tomography for the Australian region using a three-stage approach incorporating finite frequency effects

[1] A three-stage inversion technique for surface wave tomography is applied to the Australian region. The inversion procedure consists of three independent processes. In the first stage, path-specific one-dimensional (1-D) shear velocity profiles are derived from multimode waveform inversion to provide dispersion information. The information from all paths is then combined to produce multimode phase speed maps as a function of frequency. The first version of these phase speed maps is derived from linearized inversion based on the assumption of surface wave propagation along great circle paths. Subsequently, the 2-D phase speed maps are updated by including ray tracing and finite frequency effects through the influence zone around the surface wave paths over which the phase is coherent. Finally, in the third stage the 3-D shear wave speed distribution is reconstructed from the set of updated multimode phase speed maps. This three-stage inversion of surface waves has significant benefits because it is possible to incorporate multimode dispersion, off-great circle propagation, and finite frequency effects for surface waves in a common framework. The final 3-D model, which includes the effects of ray bending and finite frequency, shows improvement in the definition of the model in regions with high gradients in shear velocity, such as near tectonic boundaries, especially in eastern Australia. Despite the natural smoothing imposed by considering the influence zone around the surface wave paths, the final models still require rapid change in shear wave properties in the neighborhood of the edge of the craton

Towards constitutive equations for the deep Earth

A new formulation of constitutive equations for states of high compression is introduced for isotropic media, exploiting a separation between hydrostatic and deviatoric components in strain energy. The strain energy is represented as functions of strain invariants, with one purely volumetric component and the other which vanishes for purely hydrostatic deformation. This approach preserves the form of familiar equations of state through the volumetric component, but allows the addition of volume and pressure dependence of the shear modulus from the deviatoric term. A suitable shear modulus representation to accompany a Keane equation of state is demonstrated

Seismic structure of the mantle ; from subduction zone to craton

Seismological techniques have provided much of the currently available information on the internal structure of the Earth, and in particular on the mantle. Early studies revealed the need for an increase in seismic velocity with depth in the Earth, and by 1915 Gutenberg was able to make a good estimate of the radius of the core. Knowledge of the Earth's internal structure was refined by iterative improvement of earthquake locations and the travel times for seismic phases through the Earth, so that in 1940 Jeffreys and Bullen were able to publish an extensive set of travel-time tables based on a model of both P-wave and S-wave velocities in the mantle. Their velocity profile was intentionally as smooth as possible, but it was not possible to avoid introducing a sharp change in velocity gradient near a depth of 400 km to account for the distinct change in the slope of travel-time curves at a distance of approximately 20' from the source, for both P and S waves. Subsequent studies have refined our conception of mantle structure to reveal the presence of discontinuities in velocity and zones of strong velocity gradients, which have been correlated with mineralogical phase changes