While metamorphic reactions in subducting slabs liberate large amounts of fluids, low-frequency earthquakes (LFE) largely occur beneath the impermeable, un-metamorphosed overlying plate, and are rarely found beneath metamorphosed plates. Scientists at Tokyo Institute of Technology and Tohoku University suggest that undrained conditions are a key factor in the generation of LFEs, whereas well-drained conditions reduce pore-fluid pressures at the megathrust and inhibit LFEs and associated tremors.