Along the strike of subduction zones, tectonic tremor activity is
segmented on a geologic scale, indicating local variations of the
tremor-generating process. Here, we study how strong temporal clustering
and long-term recurrence of activity can emerge from the synchronization
of elementary tremor sources, as they interact through fluid pressure
transients. We model tremor sources as rapid openings of
low-permeability valves in the permeable fault zone channeling the
upward flow of deep metamorphic fluids. Valve openings trigger fast
pressure transients that generate seismic waves. In such a system,
tremor activity is thus shaped by unsteady fluid circulation. Using
numerical simulations of fluid flow for a large number of different
valve populations, we show that the synchronized, collective activity of
sources generates episodic activity, and that along-strike variations of
fluid flux and fluid transport properties can lead to the segmentation
of tremor activity. Strong tremor bursts that coherently activate wide
parts of the fault and recur with a long period are associated with
patches densely populated with valves and characterized by below-average
permeability. Long-term tremor episodicity emerges from the synchronous
activity of valves in such patches and is responsible for fluid-pressure
cycling at the subduction scale. In the tremor zone of the Shikoku,
Japan, subduction interface, the most temporally clustered segment
coincides with a downgoing seamount chain, suggesting that the
segmentation of the fault zone permeability, and hence of tremor
activity, could be inherited from the topography of the subducting
oceanic plate.