The traditional high-order staggered-grid finite-difference (SGFD) method has high-order accuracy in space, but only the second-order accuracy in time, which makes the traditional SGFD method suffer from a large temporal dispersion error during long-distance wave propagation. This paper develops temporal fourth- and sixth-order and spatial arbitrary evenorder SGFD schemes to model isotropic elastic wave propagation. The temporal high-order SGFD schemes have smaller temporal dispersion than the traditional temporal second-order scheme, and thus allow larger time steps to attain a similar accuracy. The developed temporal high-order SGFD schemes are applied to simulate a quasi-stress–velocity wave equation (QWE) that is derived in the framework of a$k$-space approach. A split QWE (SQWE) is further developed, and numerical simulation of SQWE results in separated P (compressional)-wave and S (shear)-wave. Theoretical computational cost analysis verifies that the numerical simulation of QWE using the temporal fourthand sixth-order SGFD schemes is more efficient than the numerical simulation of the traditional stress–velocity wave equation using the traditional temporal second-order SGFD scheme in 2-D. In 3-D, the temporal fourth-order SGFD scheme still runs faster than the traditional temporal second-order scheme; however, the temporal sixth-order scheme is more efficient only when a longer stencil length than 12 is adopted. Numerical examples confirm the correctness of the developed elastic wave modeling schemes.

Bandpass filtering is a common way to estimate ground-roll noise on land seismic data, because of the relatively low-frequency content of ground roll. However, there is usually a frequency overlap between ground roll and the desired seismic reflections that prevents bandpass filtering alone from effectively removing ground roll without also harming the desired reflections. We apply a bandpass filter with a relatively high upper bound to provide an initial imperfect separation of ground roll and reflection signal. We then apply a technique called “local orthogonalization” to improve the separation. The procedure is easily implemented, since it involves only bandpass filtering and a regularized division of the initial signal and noise estimates. We demonstrate the effectiveness of the method on an open-source set of field data.

Development of a real-time shaded rendering approach for a frequently changing viewpoint or view vector is very important in the simulation of 3-D objects in Computer-Aided Design.A new approach is proposed in this paper to meet this demand in a very efficient manner.A pre-processing phase, in which a feudal priority tree is established for all polygons of an object, and a post-processing phase, in which a rendering priority list is searched for from the feudal priority tree for a new viewpoint or view vector, are included in our approach.The most time-consuming work is finished in the pre-processing phase which only has to be executed once for an object, and the relatively simple task is left to the post-processing phase, which is repeated when the viewpoint or view vector is changed.For the pre-processing phase, a static version and a dynamic version are proposed in this paper.The one-way priority relations of all polygons are computed in the former part of the dynamic pre-processing in a more efficient way than that in the static pre-processing, but the latter part of the dynamic preprocessing is still based on the static pre-processing.A new concept of "absolute priority" is introduced to systematically reduce the polygons in which a separating plane is to be searched for so the probability of finding the separating plane is much increased.This is the basis to implement another important concept of "separating before splitting" by which the polygon splittings are much reduced.Hence the efficiency in the pre-processing and the post-processing phases is highly increased.