There is evidence of triggering of tremor by seismic waves emanating fromdistant large earthquakes. The frequency contents of triggered and ambienttremor are largely identical, suggesting that tremor does not depend directlyon the nature of the source. We show here that the model of plate dynamicsdeveloped earlier by us is an appropriate tool for describing the onset oftremor. In the framework of this model, tremor is an internal response of afault to a failure triggered by external disturbances. The model predictsgeneration of radiation in a frequency range defined by the fault parameters.Other specific features predicted are: the upper limit of the size of theemitting area is a few dozen km; tremor accompanies earthquakes and aseismicslip; the frequency content of tremor depends on the type of failure. The modelalso explains why a tremor has no clear impulsive phase, in contrast toearthquakes. A comparatively small effective normal stress (hence a high fluidpressure) is required to make the model consistent with observed tremorparameters. Our model indicates that tremor is not necessarily a superpositionof low frequency earthquakes, as commonly assumed, although the latter maytrigger them. The approach developed complements the conventional viewpointwhich assumes that tremor reflects a frictional process with low rupture speed.Essentially our model adds the hypothesis that resonant-type oscillations existinside a fault. This addition may change our understanding of the nature oftremor in general, and the methods of its identification and location inparticular.
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