caa a22 4500 47581410X CHVBK 20180406123805.0 cr unu---uuuuu 170329e20001201xx s 000 0 eng 10.1007/PL00001064 doi (NATIONALLICENCE)springer-10.1007/PL00001064 Shear Heating in Granular Layers [Elektronische Daten] [K. Mair, C. Marone] —Heat-flow measurements imply that the San Andreas Fault operates at lower shear stresses than generally predicted from laboratory friction data. This suggests that a dramatic weakening effect or reduced heat production occur during dynamic slip. Numerical studies intimate that grain rolling or localization may cause weakening or reduced heating, however laboratory evidence for these effects are sparse. We directly measure frictional resistance (μ), shear heating and microstructural evolution with accumulated strain in layers of quartz powder sheared at a range of effective stresses (σ n = 5 - 70 MPa) and sliding velocities (V = 0.01 - 10 mm/s). Tests conducted at σ n ≥ 25 MPa show strong evidence for shear localization due to intense grain fracture. In contrast, tests conducted at low effective stress (σ n = 5 MPa) show no preferential fabric development and minimal grain fracture hence we conclude that non-destructive processes such as grain rolling/sliding, distributed throughout the layer, dominate deformation. Temperature measured close to the fault increases systematically with σ n and V, consistent with a one-dimensional heat-flow solution for frictional heating in a finite width layer. Mechanical results indicate stable sliding $(\mu \sim 0.6)$ for all tests, irrespective of deformation regime, and show no evidence for reduced frictional resistance at rapid slip or high effective stresses. Our measurements verify that the heat production equation $(q =\mu \sigma_n V)$ holds regardless of localization state or fracture regime. Thus, for quasistatic velocities (V≤ 10 mm/s) and effective stresses relevant to earthquake rupture, neither grain rolling/sliding or shear localization appear to be a viable mechanism for the dramatic weakening or reduced heating required to explain the heat flow paradox. Birkhauser Verlag Basel,, 2000 Key Words: Friction, shear heating, fault strength, shear localization, fault gouge nationallicence Mair K. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. E-mail: karen@barre.mit.edu cjm@westerly.mit.edu, US aut Marone C. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. E-mail: karen@barre.mit.edu cjm@westerly.mit.edu, US aut https://doi.org/10.1007/PL00001064 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/PL00001064 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Mair K. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. E-mail: karen@barre.mit.edu cjm@westerly.mit.edu, US aut NATIONALLICENCE 700 1- Marone C. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. E-mail: karen@barre.mit.edu cjm@westerly.mit.edu, US aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer