Russian researchers have been looking at phenomena of linked mechanical and
electromagnetical properties; their goal has been to find
anomalies in electromagnetic properties (primarily currents and radiation)
induced by mechanical
anomalies (propagating seismic waves).
In mathematical physics the notion of generalized forces, coordinates, and work
functions is a powerful and mathematically elegant tool to describe the
dynamic state of a physical system. Rigorous mathematical treatments
given in Lanczos (1970) and Landau et al (1984) show that the state of a physical system can be
described by complete sets of dependent and independent generalized variables.
These variables usually do not have geometrical euclidian meaning; rather they
describe the system in an abstract space called *phase space*.
The equations describing the
evolution of the system take on canonical form in these coordinates.
Consequently mathematical concepts like Lagrange's variational principle
or Hamilton's principle also take canonical form.
In this paper I combine the ideas of elastic stresses, electric field strengths,
and entropy into a generalized stress theory (the stresses being dependent
variables) in order to describe the dynamic state of a solid body.
Such generalized stress can be
linearly related to generalized displacement, which combines elastic strains, electric displacement, and temperature.
This concept implicitly incorporates important thermodynamic principles
such as Onsager's principle.
It is a macroscopic description of rock properties and consequently
allows us to assign some average properties to the medium.
I omit the consideration of porous media, since it exceeds the scope of linear
theory.

1/13/1998