HR: 0800h
AN: T21B-0470    [Abstracts]
TI: Laboratory investigation of heat dissipation on faults during frictional sliding
AU: Renard, F
EM: francois.renard@ujf-grenoble.fr
AF: LGIT, University of Grenoble, BP 53, Grenoble, 38041 France
AU: Renard, F
EM: francois.renard@ujf-grenoble.fr
AF: Physics of Geological Processes, University of Oslo, PO box 1048, Blindern, Oslo, 0316 Norway
AU: * Mair, K
EM: karen.mair@fys.uio.no
AF: Physics of Geological Processes, University of Oslo, PO box 1048, Blindern, Oslo, 0316 Norway
AB: Heat generated during frictional sliding is an important component of the energy budget of earthquakes. Frictional heating is a potential weakening mechanism in the earth's crust. For these reasons it is highly relevant to investigate heat dissipation during faulting. We present results from new laboratory experiments where we measure heat emission during frictional sliding of simulated faults using novel thermal imaging techniques. A 3x3 cm cleaved crystal of halite (NaCl) held under constant normal load is dragged across a rough sandpaper surface at constant slip rate. Since halite is transparent to infra-red, we can monitor heat emission at the sliding surface using a high resolution infra-red camera. We also record surface evolution optically and monitor frictional resistance to sliding with accumulated slip through time. We characterize the thermal signature of a given experiment as the average heat signal of the interface and local dynamic fluctuations about that average heat. During sliding, the hard sand grains of the substrate create grooves in the weak salt by plastic deformation. These developing striations are clearly visible in the temperature records as a heat spot is produced at the tip of each groove. The spatial distribution of heat is highly heterogeneous, and our data indicate transient heat spots appearing and disappearing during sliding. These fluctuations are thought to be associated with asperity processes and there appears to be a temporal association between heat pulse events and stick slip motion as observed by sliding friction. Moreover, some regions of the surface remain relatively cold, even after a significant amount of slip, indicating that energy dissipation is highly heterogeneous over the entire fault. Our approach offers the possibility to link microscopic thermal processes with macroscopic friction and better understand how energy partitions into different deformation mechanisms during frictional sliding on faults.
DE: 7209 Earthquake dynamics (1242)
DE: 8010 Fractures and faults
DE: 8034 Rheology and friction of fault zones (8163)
SC: Tectonophysics [T]
MN: Fall Meeting 2005