The mechanism of excitation of solitary waves by friction and their influence on the stick-slip process

The modern concept of seismic process relays mainly on the model of frictional instability. We investigated stick-slip process: triggering and synchronization of instabilities in experimental spring-slider system by recording acoustic emission, accompanying the slip events. Experimental setup represents a system of two horizontally oriented plates. The supporting and the slipping blocks were prepared from basalt; the experiments were conducted with and without mechanical forcing. Presented Figure is showing a recording of acoustic pulses of one experiment (Fig 1) and one acoustic pulse in expanded form (Fig 2). In the onset of expanded acoustic recordings can be seen a pulse, which is repeated in other records also. Explanation of the nature of this pulse for us has always represented the great challenge. We guess that its existence must be associated with solitary waves. It is noted that the strain waves propagating along the block contacts occur prior to the dynamic displacement, which is the final stage of the stick-slip cycle. Soliton-type solutions are also obtained by considering the Burridge-Knopoff model of earthquake known as breathers. Breather solutions are rare and the only nonlinear wave equation is known to possess large breather solutions is the sine-Gordon equation. Soliton wave arises in the process of stick-slip, propagates along the contact surface between the plates and produces a maximum effect on the upper plate at its end point in the direction of sliding. These impacts may affect triggering of new stick-slip events. In the case of our experiment, the soliton wave emerged in the process of stick-slip process can determine the triggered events. Our goal is to develop a mathematical model of the mechanism of excitation of soliton waves in the process of friction and with it help, in the case of our experiments, to clarify the mechanism of stick-slip. It is important to generalize the above considered phenomenon for the earthquake event and to use it for explanation of triggering mechanism of the earthquake.