A universal power-law scaling exponent for fracture apertures in sandstones

Research Article| September 01, 2014 A universal power-law scaling exponent for fracture apertures in sandstones J.N. Hooker; J.N. Hooker † 1Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78713, USA2Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78713, USA †Current address: Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3AN, UK; john.hooker@earth.ox.ac.uk. Search for other works by this author on: GSW Google Scholar S.E. Laubach; S.E. Laubach 1Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78713, USA Search for other works by this author on: GSW Google Scholar R. Marrett R. Marrett 2Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78713, USA Search for other works by this author on: GSW Google Scholar Author and Article Information J.N. Hooker † 1Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78713, USA2Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78713, USA S.E. Laubach 1Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78713, USA R. Marrett 2Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78713, USA †Current address: Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3AN, UK; john.hooker@earth.ox.ac.uk. Publisher: Geological Society of America Received: 11 Jun 2013 Revision Received: 14 Feb 2014 Accepted: 30 Apr 2014 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2014 Geological Society of America GSA Bulletin (2014) 126 (9-10): 1340–1362. https://doi.org/10.1130/B30945.1 Article history Received: 11 Jun 2013 Revision Received: 14 Feb 2014 Accepted: 30 Apr 2014 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation J.N. Hooker, S.E. Laubach, R. Marrett; A universal power-law scaling exponent for fracture apertures in sandstones. GSA Bulletin 2014;; 126 (9-10): 1340–1362. doi: https://doi.org/10.1130/B30945.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract A high-resolution data set of kinematic aperture (opening displacement) of opening-mode fractures, from large (up to 2 m long) quartz-cemented sandstone samples, shows that microfractures are ubiquitous and that most natural-fracture sets are better fit by power-law size distributions than by exponential, normal, or log-normal distributions. The data set includes 3822 fractures within 68 scanlines from eight formations on three continents. Kinematic apertures were measured along scanlines using scanning electron microscope cathodoluminescence (SEM-CL) and, for field data, using a hand lens. Microtextural evidence from SEM-CL shows that power law–distributed fractures typically have crack-seal texture and are composed of opening increments having a narrow (characteristic) aperture size range. In contrast, rare non-power-law–distributed fracture populations lack crack-seal texture. Power-law exponents, as measured in one dimension, have values of –0.8 ± 0.1. Most variation among fracture sets results from power-law coefficients, which constitute a scale-invariant measure of fracture intensity. We show how observed scaling patterns can be used to improve estimations of large-fracture spacing in cases where fracture sampling is limited, as by the width of cores. The low (<1) value of the power-law scaling exponent reflects but a gentle increase in fracture frequency with decreasing size, such that microfracture abundances in core are commonly too low for statistically robust sampling. On the other hand, the consistency of the scaling exponent among fracture sets within various tectonic settings is such that the exponent can be assumed, facilitating large-fracture spacing estimations. The assumption of the scaling exponent should be supported by the presence of crack-seal texture within fractures. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.