Research Article| March 01, 2011 Size-dependent comminution, tectonic mixing, and sealing behavior of a “structurally oversimplified” fault zone in poorly lithified sands: Evidence for a coseismic rupture? F. Balsamo; F. Balsamo † Dipartimento di Scienze Geologiche, Università degli Studi Roma Tre, Rome 00146, Italy †E-mail: balsamo@uniroma3.it Search for other works by this author on: GSW Google Scholar F. Storti F. Storti Dipartimento di Scienze Geologiche, Università degli Studi Roma Tre, Rome 00146, Italy Search for other works by this author on: GSW Google Scholar Author and Article Information F. Balsamo † Dipartimento di Scienze Geologiche, Università degli Studi Roma Tre, Rome 00146, Italy F. Storti Dipartimento di Scienze Geologiche, Università degli Studi Roma Tre, Rome 00146, Italy †E-mail: balsamo@uniroma3.it Publisher: Geological Society of America Received: 28 May 2009 Revision Received: 20 Jan 2010 Accepted: 21 Jan 2010 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2011 Geological Society of America GSA Bulletin (2011) 123 (3-4): 601–619. https://doi.org/10.1130/B30099.1 Article history Received: 28 May 2009 Revision Received: 20 Jan 2010 Accepted: 21 Jan 2010 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation F. Balsamo, F. Storti; Size-dependent comminution, tectonic mixing, and sealing behavior of a “structurally oversimplified” fault zone in poorly lithified sands: Evidence for a coseismic rupture?. GSA Bulletin 2011;; 123 (3-4): 601–619. doi: https://doi.org/10.1130/B30099.1 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 We studied a structurally oversimplified, extensional fault zone developed in poorly lithified, quartz-rich, high-porosity sandy sediments of the seismically active Crotone Basin (southern Italy). The fault zone consists of a cm-thick, discrete fault core embedded in virtually undeformed wall sediments. By combining grain size, shape, and microstructural analyses with mineralogical analyses and permeability measurements, we investigated the influence of initial sedimentological characteristics of sands on the final faulted granular products and related hydrologic properties. Faulting produces a general grain-size and porosity reduction by changing both the grain-size and shape distributions. We document a combination of intragranular fracturing, spalling, and flaking of grain edges in the fault core, which do not depend on grain mineralogy. The dominance of cataclasis, also confirmed by fractal dimensions >2.6, is generally not expected at a deformation depth <1 km. Initial grain size exerts a fundamental control on the comminution process and on the resulting permeability variations up to four orders of magnitude. Coarse-grained sand shows a much higher comminution intensity, grain-shape variations, and permeability drop than fine-grained sands. This is because coarser aggregates have (1) fewer grain-to-grain contacts for a given area, which results in higher stress concentration at contact points, and (2) a higher probability of preexisting, intragranular microstructural defects that result in a lower grain strength. The peculiar structural architecture, the dominance of cataclasis over nondestructive particulate flow, and the compositional variations of clay minerals in the fault core strongly suggest that the studied fault zone developed by a coseismic rupture. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.