Oceanic transform faults, connecting offset mid-ocean spreading centres, rupture quasi-periodically in earthquakes up to about magnitude M 7.0 that are often preceded by foreshocks. In addition to seismic slip, a large portion of slip takes place as aseismic creep, which likely influences initiation of large earthquakes. Although oceanic transform faults are one of the major types of plate boundaries, the exact mode of slip and interaction between the seismic and aseismic motion remains unclear. Here we present a detailed model of the mode of slip at oceanic transform faults based on data acquired from a recent temporary deployment of ocean-bottom seismometers at the Blanco Transform Fault and existing regional and teleseismic observations. In the model, the crustal part of the fault is brittle and fully seismically coupled, while the fault in the mantle, shallower than the depth of the 600 °C isotherm, creeps partially and episodically. The creep activates small asperities in the mantle that produce seismic swarms. Both mantle and the crustal zones release most of the plate-motion strain during large-magnitude earthquakes. Large earthquakes appear to be preceded by a brief episode of shallow mantle creep, accompanied by seismic swarms, which explains the observation of foreshocks and shows that mantle creep likely influences initiation of large seismic events.
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The OBS dataset is archived at the IRIS Data Management System (http://www.iris.edu). X9 is the network code for the Plate Boundary Evolution and Physics at an Oceanic Transform Fault System project32; 7D is the network code for the Cascadia Initiative Community Experiment – OBS component data33. Raw bathymetry data, used in Fig. 1 and Supplementary Fig. 1, are available from the authors.
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Braunmiller, J. & Nábělek, J. Segmentation of the Blanco Transform Fault Zone from earthquake analysis: complex tectonics of an oceanic transform fault. J. Geophys. Res. Solid Earth 113, B07108 (2008).
Embley, R. W. & Wilson, D. S. Morphology of the Blanco Transform Fault Zone-NE Pacific: implications for its tectonic evolution. Mar. Geophys. Res. 14, 25–45 (1992).
Boettcher, M. S. & McGuire, J. J. Scaling relations for seismic cycles on mid-ocean ridge transform faults. Geophys. Res. Lett. 36, L21301 (2009).
McGuire, J. J. et al. Variations in earthquake rupture properties along the Gofar transform fault, East Pacific Rise. Nat. Geosci. 5, 336–341 (2012).
Roland, E., Behn, M. D. & Hirth, G. Thermal‐mechanical behavior of oceanic transform faults: implications for the spatial distribution of seismicity. Geochem. Geophys. Geosyst. 11, Q07001 (2010).
Boettcher, M. S., Hirth, G. & Evans, B. Olivine friction at the base of oceanic seismogenic zones. J. Geophys. Res. Solid Earth 112, B01205 (2007).
Lohman, R. B. & McGuire, J. J. Earthquake swarms driven by aseismic creep in the Salton Trough, California. J. Geophys. Res. Solid Earth 112, B04405 (2007).
Linde, A. T., Gladwin, M. T., Johnston, M. J. S., Gwyther, R. L. & Bilham, R. G. A slow earthquake sequence on the San Andreas fault. Nature 383, 65–68 (1996).
Roland, E. & McGuire, J. J. Earthquake swarms on transform faults. Geophys. J. Int. 178, 1677–1690 (2009).
Scholz, C. H. The Mechanics of Earthquakes and Faulting (Cambridge Univ. Press, Cambridge, 1990).
Francis, T. Serpentinization faults and their role in the tectonics of slow spreading ridges. J. Geophys. Res. Solid Earth 86, 11616–11622 (1981).
Kohli, A. H., Goldsby, D. L., Hirth, G. & Tullis, T. Flash weakening of serpentinite at near‐seismic slip rates. J. Geophys. Res. Solid Earth 116, B03202 (2011).
Reinen, L. A. Seismic and aseismic slip indicators in serpentinite gouge. Geology 28, 135–138 (2000).
Guillot, S., Schwartz, S., Reynard, B., Agard, P. & Prigent, C. Tectonic significance of serpentinites. Tectonophysics 646, 1–19 (2015).
Dziak, R. P. et al. Recent tectonics of the Blanco Ridge, eastern Blanco Transform Fault Zone. Mar. Geophys. Res. 21, 423–450 (2000).
Boettcher, M. S. & Jordan, T. H. Earthquake scaling relations for mid‐ocean ridge transform faults. J. Geophys. Res. Solid Earth 109, B12302 (2004).
Okal, E. A. & Langenhorst, A. R. Seismic properties of the Eltanin Transform System, South Pacific. Phys. Earth Planet. Interiors 119, 185–208 (2000).
Bird, P., Kagan, Y. Y. & Jackson, D. D. in Plate Boundary Zones (eds Stein, S. S. & Freymueller, J. T.) 203–218 (AGU, Washington DC, 2002).
McGuire, J. J. Seismic cycles and earthquake predictability on East Pacific Rise transform faults. Bull. Seismol. Soc. Am. 98, 1067–1084 (2008).
Sykes, L. R. & Ekström, G. Earthquakes along Eltanin transform system, SE Pacific Ocean: fault segments characterized by strong and poor seismic coupling and implications for long-term earthquake prediction. Geophys. J. Int. 188, 421–434 (2012).
McGuire, J. J. Immediate foreshock sequences of oceanic transform earthquakes on the East Pacific Rise. Bull. Seismol. Soc. Am. 93, 948–952 (2003).
McGuire, J. J., Boettcher, M. S. & Jordan, T. H. Foreshock sequences and short-term earthquake predictability on East Pacific Rise transform faults. Nature 434, 457–461 (2005).
McGuire, J. J., Ihmle, P. F. & Jordan, T. H. Time-domain observations of a slow precursor to the 1994 Romanche transform earthquake. Science 274, 82–85 (1996).
Abercrombie, R. E. & Ekström, G. Earthquake slip on oceanic transform faults. Nature 410, 74–77 (2001).
Wilson, D. S. Confidence intervals for motion and deformation of the Juan de Fuca Plate. J. Geophys. Res. Solid Earth 98, 16053–16071 (1993).
DeMets, C., Gordon, R. G. & Argus, D. F. Geologically current plate motions. Geophys. J. Int. 181, 1–80 (2010).
Pavlis, G. L., Vernon, F., Harvey, D. & Quinlan, D. The generalized earthquake-location (GENLOC) package: an earthquake-location library. Comput. Geosci. 30, 1079–1091 (2004).
Waldhauser, F. & Ellsworth, W. L. A double-difference earthquake location algorithm: method and application to the northern Hayward Fault, California. Bull. Seismol. Soc. Am. 90, 1353–1368 (2000).
De Rubeis, V., Loreto, V., Pietronero, L. & Tosi, P. in Modelling Critical and Catastrophic Phenomena in Geoscience (eds Bhattacharyya, P.& Chakrabarti, B. K.) 259–279 (Springer, Berlin Heidelberg, 2006).
Brune, J. N. Tectonic stress and the spectra of seismic shear waves from earthquakes. J. Geophys. Res. 75, 4997–5009 (1970).
Hanks, T. C. & Kanamori, H. A moment magnitude scale. J. Geophys. Res. Solid Earth 84, 2348–2350 (1979).
Nábělek, J., Braunmiller, J. Plate boundary evolution and physics at an oceanic transform fault system. International Federation of Digital Seismograph Networks https://doi.org/10.7914/SN/X9_2012 (2012).
IRIS OBSIP Cascadia Initiative Community Experiment - OBS component. International Federation of Digital Seismograph Networks https://doi.org/10.7914/SN/7D_2011 (2011).
The seismic stations for the project were provided by the Ocean Bottom Seismograph Instrument Pool (http://www.obsip.org), funded by the National Science Foundation (NSF). This research was supported by NSF grants OCE-1031858, OCE-1131767 and OCE-1737073. We thank the crews of RV Melville and RV Oceanus, OBSIP technicians and volunteers who contributed to data collection.
Supplementary Figures, Supplementary Tables.
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Nature Geoscience (2019)