Hypothesis of spontaneous conversion (in earthquake foci)

The earlier introduced hypothesis of deformational conversion is now presen ted as a hypothesis of spontaneous frontal conversion (SFC hypothesis). The term "conversion" denotes transformation of decreasing elastic strain into residual irreversible deformation, the process which, according to Maxwell , is the essence of irreversible deformation (the idea of Maxwell's convers ion is the main focus in the paper). The SFC hypothesis is as follows: The unevenly deforming Earth involves ove rdeformed zones where frontal conversion can arise at any point at any time and develop along a front that moves within the zone. The main objective of the work was to model a medium favorable for developm ent of SFC. The proposed model excludes the states of above-limit elastic d eformation, puts constraints on conversion on the conversion front, and imp lies a relationship between density of elastic energy W and parameters of t he medium, which is linear in terms of geometry and nonlinear in terms of p hysics. A specific problem of SFC in a confined cylinder, posed and investigated se parately, allowed the following inferences: (a) the over-deformed state exists if the medium is physically nonlinear an d its parameters remain within a certain domain S; (b) the velocity of c-front can vary from zero to highest possible for elas tic waves in a cylinder, In function of parameters of the medium within the domain S; (c) the conversion front is pre-sonic, is it preceded by a precursor wave w hich has a smooth arrival (u similar to t(2)) and is a compressional wave i n a compressed cylinder and a,,wave of rarefaction" under extension; (d) conversion in a cylinder where the medium parameters are beyond the dom ain S constitutes a separate specific problem. In the course of further studies it is supposed to work for the following o bjectives: (1) systematization of relevant seismological data; (2) identifi cation of other forms of thermal conversion and processing of the available experiment data; (3) gain of more experience in theoretical investigation of frontal conversion (for other situations and other W functions), improve ment and experimental testing of the model. and further refinement of W Fun ction; (4) search for the physical background of the chosen model constrain ts; (5) practical testing of the model in mining.