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GEOPHYSICAL RESEARCH LETTERS, VOL. 29, NO. 24, 2207, doi:10.1029/2002GL015612, 2002

Evidence for weak oceanic transform faults

Mark D. Behn

MIT-WHOI Joint Program, Woods Hole, Massachusetts, USA


Jian Lin

Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA


Maria T. Zuber

Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA


Abstract

We present the results of a series of 3-D boundary element calculations to investigate the effects of oceanic transform faults on stress state and fault development at adjacent mid-ocean ridge spreading centers. We find that the time-averaged strength of transform faults is low, and that on time scales longer than a typical earthquake cycle transform faults behave as zones of significant weakness. Specifically, mechanical coupling of only ∼5% best explains the observed patterns of strike-slip and oblique normal faulting near a ridge-transform intersection. On time scales shorter than a typical earthquake cycle, transient “locked” periods can produce anomalous reverse faulting similar to that observed at the inside corner (IC) of several slow-spreading ridge segments. Furthermore, we predict that extensional stresses will be suppressed at the IC due to the shear along the transform resisting ridge-normal extension. This implies that an alternative mechanism is necessary to explain the preferential normal fault growth and enhanced microseismicity observed at many ICs.

Published 27 December 2002.

Index Terms: 3035 Marine Geology and Geophysics: Midocean ridge processes.

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Citation: Behn, M. D., J. Lin, and M. T. Zuber (2002), Evidence for weak oceanic transform faults, Geophys. Res. Lett., 29(24), 2207, doi:10.1029/2002GL015612.