Nonlinear Processes in Geophysics www.nonlin-processes-geophys.net 1023-5809 1607-7946 3 2 1996 10.5194/npg-3-89-1996 http://www.nonlin-processes-geophys.net/3/89/1996/ http://www.nonlin-processes-geophys.net/3/89/1996/npg-3-89-1996.html http://www.nonlin-processes-geophys.net/3/89/1996/npg-3-89-1996.pdf 89 101 0000-00-00 A new theoretical paradigm to describe hysteresis, discrete memory and nonlinear elastic wave propagation in rock K. R. McCall R. A. Guyer Los Alamos National Laboratory, Los Alamos, New Mexiko Present address Department of Physics, University of Nevada, Reno, Nevada Present address Department of Physics and Astronomy, University of Massachusetts, Amherst, Massachusetts The velocity of sound in rock is a strong function of pressure, indicating that wave propagation in rocks is very nonlinear. The quasistatic elastic properties of rocks axe hysteretic, possessing discrete memory. In this paper a new theory is developed, placing all of these properties (nonlinearity, hysteresis, and memory) on equal footing. The starting point of the new theory is closer to a microscopic description of a rock than the starting point of the traditional five-constant theory of nonlinear elasticity. However, this starting point (the number density <I>Ï?</I> of generic mechanical elements in an abstract space) is deliberately independent of a specific microscopic model. No prejudice is imposed as to the mechanism causing nonlinear response in the microscopic mechanical elements. The new theory (1) relates suitable stress-strain measurements to the number density <I>Ï?</I> and (2) uses the number density <I>Ï?</I> to find the behaviour of nonlinear elastic waves. Thus the new theory provides for the synthesis of the full spectrum of elastic behaviours of a rock. Early development of the new theory is sketched in this contribution.