No description available.

A search for the effects of anisotropy on seismic body-waves predicted by theory is described. Preliminary studies were based on long-period data from the WWSSN, HGLP and SRO networks. These showed that data from the WWSSN network are unsuitable for anisotropy studies because of features in the geometry of the recording system which lead to misalignment of the digitizer relative to the galvanometer-swing (which it is not always possible to correct) and the fact that the horizontal components are not always well matched. Digital data from the HGLP (recorded after 1976) and SRO networks are more suitable for anisotropy studies but eventually it was found that the anisotropic differences are too small to be resolved by long-period instruments. Analysis of short-period teleseismic shear-waves observed at LRSM stations located in United States and southern Canada has revealed shear-wave splitting diagnostic of anisotropy somewhere along the path. The shear-wave splitting is often seen as two separate shear-wave arrivals on the rotated horizontal components. All cases of shear-wave splitting are indicated by an abrupt change in the direction of particle-motion in the horizontal plane. A selection of seismograms and associated particlemotion diagrams is presented in order to illustrate shear-wave splitting. The polarizations of the first arrival shear-waves and the delays between the shear-wave arrivals were measured and are presented in the form of stereograms. The maximum shear-wave delay observed is 2.75 seconds and on the basis of this, we calculate the thickness of the anisotropic layer to be 248 kms for a model with 4.5% differential shearwave velocity anisotropy. For a model with much higher differential shear-wave velocity anisotropy (8.4%), the thickness of the layer is only 136 kms. Our results do not allow us to constrain the depth to the top of the anisotropic layer, although on the basis of other studies we believe the anisotropic layer to be situated immediately below the Mohorovicic discontinuity. The polarizations are broadly similar to those obtained theoretically for the y- and z-cuts of olivine, transversely isotropic olivine and mixture of transversely isotropic olivine/isotropic material. On the basis of this, we tentatively identify N50°E as a direction of symmetry and note that it is approximately parallel to the absolute motion of the North-American plate. We therefore suspect a causal relationship between plate motion and the generation of anisotropy. The most likely hypothesis is that as the continental lithosphere moves across the asthenosphere, the drag on the lithosphere sets up a horizontal compression in the direction of motion of the lithosphere relative to the asthenosphere and olivine crystals align by {Okl} [100] pencil glide so that the a-axis points into the direction of plate motion while the b and c axes form girdles perpendicular to the a-axis. This would result in transverse isotropy with the axis of symmetry horizontal, an orientation which is consistent with our results. The existence of anisotropy in the upper mantle has implications for other seismological studies. In particular, focal mechanism studies which rely solely on S-wave polarizations will be erroneous and studies of travel-time residuals will need to take account of the anisotropy.

No description available.

The phenomenon of photochemical initiation of gaseous detonation waves has been experimentally and theoretically investigated. In the experiments, the flash photolysis technique has been employed and the initiation phenomenon has been directly observed through schlieren photography, while in the theoretical phase, the non-steady reacting flow-field of a photochemically ignited gas mixture has been numerically analyzed. The results conclusively show that the direct detonation initiation can be generated by an intense ultra-violet radiation, and it is shown that the initiation mechanism is mainly attributed to the rapid shock wave amplification occurring in a non-uniformly photo-dissociating gas mixture. It was found that the shock wave amplification is due to the coherent energy release from the non-uniformly reacting gas mixture to the shock wave and that the induction time gradient field generated by the flash photolysis plays an important role in the shock amplification process. / Further insight into the fundamental mechanisms of shock wave amplification has been obtained by considering a relatively simple theoretical model. This model illustrates the important role of the induction time gradient field in the shock wave amplification. Finally the concept of shock wave amplification in an induction time gradient field has been further extended to include the problem of transition to detonation in a non-uniformly preheated mixture.

Typescript. / Thesis (Ph.D.)--University of Hawaii, 1985. / Bibliography: leaves 132-136. / Photocopy. / xxiii, 136 leaves, bound ill. 29 cm

Thesis (M.S.)--University of Hawaii at Manoa, 2007. / Includes bibliographical references (leaves 65-71). / xii, 71 leaves, bound ill. (some col.), maps 29 cm

Thesis (Ph. D.)--University of Washington, 1989. / Vita. Includes bibliographical references (leaves [182]-185).

Thesis (Ph. D.)--University of Adelaide, Dept. of Applied Mathematics, 1993. / Includes bibliographical references (leaves 117-126).

Thesis (M.Sc.) - Dept. of Mathematical Physics, University of Adelaide, 1982. / Typescript (photocopy).

Thesis (Ph.D.) -- University of Adelaide, Dept. of Physics, 2000? / Copies of author's previously published articles inserted. Bibliography: p. 227-245.