A new method of fully nonlinear waveform fitting to measure interstation phase speeds and amplitude ratios is developed and applied to USArray. The Neighbourhood Algorithm is used as a global optimizer, which efficiently searches for model parameters that fit two observed waveforms on a common great-circle path by modulating the phase and amplitude terms of the fundamental-mode surface waves. W…

The determination of near-surface attenuation for hard rock sites is an important issue in a wide range of seismological applications, particularly seismic hazard analysis. In this article we choose six hard to very-hard rock sites (Vs30 1030–3000ms–1) and apply a range of analysis methods to measure the observed attenuation at distance based on a simple exponential decay model with whole-p…

In most numerical simulations of the Earth’s core the dynamo resides outside the tangent cylinder and may be crudely classified as being of the α2 type. In this region the flow comprises a sea of thin columnar vortices aligned with the rotation axis, taking the form of alternating cyclones and anticyclones. The dynamo is thought to be driven by these columnar vortices within which the f…

Previous studies of Earth rotation perturbations due to ice-age loading have predicted a slow secular drift of the rotation axis relative to the surface geography (i.e. true polar wander, TPW) of order of several degrees over the Plio-Pleistocene. It has been argued that this drift and the change in the geographic distribution of solar insolation that it impliesmay have been responsible for imp…

A computational method is given for solving the forward modelling problem for transient electromagnetic exploration. Its key features are the discretization of the quasi-static Maxwell’s equations in space using the first-kind family of curl-conforming N´ed´elec elements combined with time integration using rational Krylov methods. We show how rational Krylov methods can also be used to sol…

NEWAGE is a direction-sensitive dark matter search experiment using a micro-time-projection chamber filled with CF4 gas. Following our first underground measurement at Kamioka in 2008, we developed a new detector with improved sensitivity, NEWAGE-0.3b’. NEWAGE-0.3b’ has twice the target volume of the previous detector, a lower energy threshold, and an improved data acquisition system. In 2…

We consider the possibility of enhancing the inflationary tensor mode by introducing a spectator scalar field with a small sound speed which induces gravitational waves as a second-order effect.We analytically obtain the power spectra of gravitational waves and curvature perturbation induced by the spectator scalar field. We find that the small sound speed amplifies the curvature perturbation m…

Seismic full waveform inversion is an objective method to estimate elastic properties of the subsurface and is an important area of research, particularly in seismic exploration community. It is a data-fitting approach, where the difference between observed and synthetic data is minimized iteratively. Due to a very high computational cost, the practical implementation of waveform inversion has …

The study of the influence of rock fabric and porefluid distribution on the seismic wavefield is important for the prediction and detection of reservoir properties such as lithology and fluid saturation. Wave-induced local fluid flow (WILFF), which is affected by local heterogeneities of the pore structure and fluid saturation, is believed to be the main mechanism to explain the measured attenu…

With the use of two kinds of boson operators, a new boson representation of the su(2)-algebra is proposed. The basic idea comes from the pseudo su(1, 1)-algebra recently given by the present authors [Y. Tsue et al., Prog. Theor. Exp. Phys. 2013, 103D04 (2013)]. It forms a striking contrast to the Schwinger boson representation of the su(2)-algebra, which is also based on two kinds of bosons. I…