Periodic Pulsing of Characteristic Microearthquakes on the San Andreas Fault

Deep fault slip information from characteristically repeating microearthquakes reveals previously unrecognized patterns of extensive, large-amplitude, long-duration, quasiperiodic repetition of aseismic events along much of a 175-kilometer segment of the central San Andreas fault.Pulsing occurs both in conjunction with and independent of transient slip from larger earthquakes.It extends to depths of ∼10 to 11 kilometers but may be deeper, and it may be related to similar phenomena occurring in subduction zones.Over much of the study area, pulse onset periods also show a higher probability of larger earthquakes, which may provide useful information for earthquake forecasting.