Modelling of the fractal structure of a geophysical field

A study has been conducted about the fractal structure (FS) of the seismic rate in block rocks constituted by a granitic layer heated to 400 degrees C and doubled by a sandstone layer. A pair of stress concentrators has been inserted within the center of the block under an angle of 35 degrees with the vertical axis of the pattern, in order to favour the shearing rupture. This construction is a model of one part of the crust where toe can have a releasing of normal seisms. We have applied a new technique of biaxial loading of samples. This has permitted, contrary to traditional experiments, to prolong in time the stage of formation and evolution of the rupture and to study in detail the step of intense interaction of acoustic events. The acoustic rate consists of three main steps: dispersive releasing of acoustic emission (AE); critical concentration of acoustic events and the formation of the focus; lastly, the evolution of this focus in order to give birth to the main rupture. The parameter K-r of rupture concentration decreases until 5-8, the b value the dimension fractal D decreases and the relation D approximate to 3b is interrupted during the FS genesis.