Abstract The first in this series, this volume contains several engineering geology articles that are still applicable and useful today: Petrography Applied to Portland-Cement Concrete, by Mielenz; Engineering Aspects of Sediment Transport, by Bruun (includes section on Biological Aspects, by Lackey); Photo Analysis and Interpretation in Engineering Geology Investigations, by Mollard; Engineering Geology of Radioactive Waste Disposal, by de Laguna; Engineering Seismology, by Neumann; Sand and Gravel, by Lenhart; Review of USSR Publications in Selected Fields of Engineering Soil Science, by Drashevska; and Stabilization of Rock by Bolting, by Thomas.

Abstract The first in this series, this volume contains several engineering geology articles that are still applicable and useful today: Petrography Applied to Portland-Cement Concrete, by Mielenz; Engineering Aspects of Sediment Transport, by Bruun (includes section on Biological Aspects, by Lackey); Photo Analysis and Interpretation in Engineering Geology Investigations, by Mollard; Engineering Geology of Radioactive Waste Disposal, by de Laguna; Engineering Seismology, by Neumann; Sand and Gravel, by Lenhart; Review of USSR Publications in Selected Fields of Engineering Soil Science, by Drashevska; and Stabilization of Rock by Bolting, by Thomas.

Abstract Evaluating the performance of finite-difference algorithms typically uses a technique known as von Neumann analysis. For a given algorithm, application of the technique yields both a dispersion relation valid for the discrete timespace grid and a mathematical condition for stability. In practice, a major shortcoming of conventional von Neumann analysis is that it can be applied only to an idealized numerical model — that of an infinite, homogeneous whole space. Experience has shown that numerical instabilities often arise in finite-difference simulations of wave propagation at interfaces address this issue, I generalize von Neumann analysis for a model of two half-spaces. I perform the analysis for the case of acoustic wave propagation using a standard staggered-grid finite-difference numerical scheme. By deriving expressions for the discrete reflection and transmission coefficients, I study under what conditions the discrete reflection and transmission coefficients become unbounded. I find that instabilities encountered in numerical modeling near interfaces with strong material contrasts are linked to these cases and develop a modified stability criterion that takes into account the resulting instabilities. I test and verify the stability criterion by executing a finite-difference algorithm under conditions predicted to be stable and unstable.