Acoustics of stick-slip deformation under external forcing: the model of seismic process synchronization

Essential dynamical changes, such as synchronization, different types of resonances, triggering etc. caused by relatively small comparing to external influences, are encountered in various fields, from mechanics to biological and even social processes. Thus it is only natural that similar phenomena are observed in many geophysical fields, as the Earth is embedded in the oscillating field of different origin with extremely wide range of frequencies, from seconds to months and years. For example there are a lot of observations that seismic activity is coupled of such weak oscillating fields as Earth tides, solar activity, atmospheric pressure, electromagnetic pulses (storms), seasonal variations, and reservoir exploitation. The intensity of stress, invoked by these superimposed periodical oscillations is as a rule much smaller than that of the main driving force - tectonic stress. Nevertheless, finally, this weak interaction may invoke mentioned phenomena, (e.g. triggering/synchronization), or, at least, change (increase) level of ordering of the system behavior in the time domain (so called phase synchronization). We reproduced these effects in laboratory conditions and it turns out that mechanical or electromagnetic (EM) forcing is a flexible tool for study of triggering and phase synchronization (PS) phenomena in laboratory slider experiments. In the paper, the results of laboratory and field experiments on the mechanical or electromagnetic (EM) initiation and synchronization of mechanical instability (slip) of a slider-spring system are presented. Slip events were recorded as acoustic emission bursts.