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Showing 1–9 of 9 results
Advanced filters: Author: David A. Lockner Clear advanced filters

  • Earthquake instability has long been attributed to fault weakening during accelerated slip, but what are the mechanisms that control this weakening? Here laboratory evidence is presented for the dynamic weakening of faults that are sheared at velocities approaching earthquake slip rates. The experimental faults, made from solid granite blocks, quickly wore to form a fine-grain rock powder, known as gouge, which reduced the faults' strength. It is concluded that only newly formed gouge can weaken the experimental faults.

    • Ze’ev Reches
    • David A. Lockner
    Research
    Nature
    Volume: 467, P: 452-455

    • David Jones
    News & Views
    Nature
    Volume: 359, P: 678

  • This study reports on laboratory-strength measurements of fault core materials from a drill hole located northwest of Parkfield, California, near the southern end of a creeping zone of the San Andreas fault. It is found that the fault is profoundly weak at this location and depth, owing to the presence of the smectite clay mineral saponite—one of the weakest phyllosilicates known. These findings provide strong evidence that deformation of the mechanically unusual creeping portions of the San Andreas fault system is controlled by the presence of weak minerals rather than by high fluid pressure or other proposed mechanisms.

    • David A. Lockner
    • Carolyn Morrow
    • Stephen Hickman
    Research
    Nature
    Volume: 472, P: 82-85

  • Shear strength of smectite clays depends on the size of the interlayer cation suggest lab-based experiments and theoretical calculations. Whereas sodium ions fit within exchange site cavities, larger potassium ions do not and enhance friction.

    • Hiroshi Sakuma
    • David A. Lockner
    • Nicholas C. Davatzes
    ResearchOpen Access
    Communications Earth & Environment
    Volume: 3, P: 1-8