1. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, and
2. MIT-Woods Hole Oceanographic Institution Joint Program, Woods Hole, Massachusetts 02543-1541, USA
3. Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-7042, USA

Correspondence to: Jeffrey J. McGuire¹ Correspondence and requests for materials should be addressed to J.J.McG. (Email: jmcguire@whoi.edu).

Abstract

East Pacific Rise transform faults are characterized by high slip rates (more than ten centimetres a year), predominately aseismic slip and maximum earthquake magnitudes of about 6.5. Using recordings from a hydroacoustic array deployed by the National Oceanic and Atmospheric Administration, we show here that East Pacific Rise transform faults also have a low number of aftershocks and high foreshock rates compared to continental strike-slip faults. The high ratio of foreshocks to aftershocks implies that such transform-fault seismicity cannot be explained by seismic triggering models in which there is no fundamental distinction between foreshocks, mainshocks and aftershocks. The foreshock sequences on East Pacific Rise transform faults can be used to predict (retrospectively) earthquakes of magnitude 5.4 or greater, in narrow spatial and temporal windows and with a high probability gain. The predictability of such transform earthquakes is consistent with a model in which slow slip transients trigger earthquakes, enrich their low-frequency radiation and accommodate much of the aseismic plate motion.

1. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, and
2. MIT-Woods Hole Oceanographic Institution Joint Program, Woods Hole, Massachusetts 02543-1541, USA
3. Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-7042, USA

Correspondence to: Jeffrey J. McGuire¹ Correspondence and requests for materials should be addressed to J.J.McG. (Email: jmcguire@whoi.edu).

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