Theory of gravity instability with variable overburden and compaction

The gravitational instability of a simple two‐layered medium resting on a rigid base has been treated in terms of the analog model of Biot. In order to avoid complications of purely mathematical nature which are unrelated to the physics of the process of instability and do not affect the results significantly, the analysis is presented for the two‐dimensional case. It is shown that such a system is unstable if the density contrast Δρ between the top layer (overburden) and the bottom layer (salt) is positive. The physically important parameters of the instability are the viscosity ratio and the thickness ratio between overburden and salt and the relative density contrast Δρ/ρ1. These parameters determine the amplification rate of a given initial sinusoidal perturbation of wavelength L of the overburden‐salt interface. For the purpose of isolating the role of each parameter and to provide an understanding of the underlying mechanics, several tables are presented which show the influence of each of these par...