HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (43) Citing Articles via Google Scholar Google Scholar Articles by Sibson, R. H. Search for Related Content GeoRef GeoRef Citation

Thickness of the Seismic Slip Zone

Department of Geology
University of Otago
P.O. Box 56
Dunedin 9001
New Zealand

This article reviews geologic and other evidence constraining the thickness of the principal slip zone (PSZ) that accommodates the bulk of coseismic shear displacement during an individual rupture event. Surface deformation from rupturing may occupy swaths tens of meters or more in width, but trenches across active faults generally reveal that incremental slip is accommodated by a PSZ that is tens of centimeters or less in thickness. Geomorphic evidence, coupled with the observations from trenching, suggest a PSZ may stay well localized for distances of several kilometers through many rupture episodes. Mine exposures and exhumed fault zones demonstrate that PSZs separating different lithologies within the "fault core," although contained within "damage zones" of variably fractured rock ranging up to hundreds of meters in thickness, often comprise just a few centimeters of gouge/ultracataclasite that have accommodated large finite displacements (>1 km). Microstructural studies demonstrate incremental slip localized still further down to 1–10 mm, as do other fault-rock assemblages (slickensides and slickenfibers, fault-veins of pseudotachylyte friction-melt, intravein septa in hydrothermal fault infills). The accumulated evidence indicates that localization of coseismic shearing to less than 10 cm on planar faults is widespread throughout the crustal seismogenic zone, with extreme localization to less than 1 cm not uncommon. However, some distributed coseismic shear may also develop, especially at rupture irregularities.

Coseismic reduction of shear resistance from friction-melting (T 1000°C) or from transient thermal pressurization of aqueous fluids (T 100°C) requires slip during moderate-to-large earthquakes (u > 1 m) to be restricted to narrow zones, respectively a few centimeters or tens of centimeters in thickness. Given the evidence for slip localization, the apparent scarcity of pseudotachylyte suggests either that seismic friction-melting is a rare phenomenon, or that pseudotachylyte is only rarely preserved in recognizable form within mature hydrated fault zones.

This article has been cited by other articles:

				M. Suter Structural Configuration of the Otates Fault (Southern Basin and Range Province) and Its Rupture in the 3 May 1887 MW 7.5 Sonora, Mexico, Earthquake Bulletin of the Seismological Society of America, December 1, 2008; 98(6): 2879 - 2893. [Abstract] [Full Text] [PDF]

				V. S. CRONIN, M. MILLARD, L. SEIDMAN, and B. BAYLISS The Seismo-Lineament Analysis Method (SLAM): A Reconnaissance Tool to Help Find Seismogenic Faults Environmental and Engineering Geoscience, August 1, 2008; 14(3): 199 - 219. [Abstract] [Full Text] [PDF]

				K. Wang and J. He Effects of Frictional Behavior and Geometry of Subduction Fault on Coseismic Seafloor Deformation Bulletin of the Seismological Society of America, April 1, 2008; 98(2): 571 - 579. [Abstract] [Full Text] [PDF]

				C. A. J. Wibberley, G. Yielding, and G. Di Toro Recent advances in the understanding of fault zone internal structure: a review Geological Society, London, Special Publications, January 1, 2008; 299(1): 5 - 33. [Abstract] [Full Text] [PDF]

				S. Boutareaud, C. A. J. Wibberley, O. Fabbri, and T. Shimamoto Permeability structure and co-seismic thermal pressurization on fault branches: insights from the Usukidani fault, Japan Geological Society, London, Special Publications, January 1, 2008; 299(1): 341 - 361. [Abstract] [Full Text] [PDF]

				N. H. Woodcock, J. A. D. Dickson, and J. P. T. Tarasewicz Transient permeability and reseal hardening in fault zones: evidence from dilation breccia textures Geological Society, London, Special Publications, January 1, 2007; 270(1): 43 - 53. [Abstract] [PDF]

				M. Rosener and Y. Geraud Using physical properties to understand the porosity network geometry evolution in gradually altered granites in damage zones Geological Society, London, Special Publications, January 1, 2007; 284(1): 175 - 184. [Abstract] [Full Text] [PDF]

				R.W. Graymer, D.A. Ponce, R.C. Jachens, R.W. Simpson, G.A. Phelps, and C.M. Wentworth Three-dimensional geologic map of the Hayward fault, northern California: Correlation of rock units with variations in seismicity, creep rate, and fault dip Geology, June 1, 2005; 33(6): 521 - 524. [Abstract] [Full Text] [PDF]

				J. P.T. Tarasewicz, N. H. Woodcock, and J. A. D. Dickson Carbonate dilation breccias: Examples from the damage zone to the Dent Fault, northwest England GSA Bulletin, May 1, 2005; 117(5-6): 736 - 745. [Abstract] [Full Text] [PDF]

				A. Lin, C.-T. Lee, T. Maruyama, and A. Chen Meso- and Microstructural Analysis of Coseismic Shear Zone of the 1999 MW 7.6 Chi-Chi Earthquake, Taiwan Bulletin of the Seismological Society of America, April 1, 2005; 95(2): 486 - 501. [Abstract] [Full Text] [PDF]