Shear Zones
• Have a look at Davis and Reynolds, Chapter 9
Shear Zones
Shear Zones
Shear zones
• Brittle or ductile– Brittle shear zone = fault zone
• Tabular or sheet like, planar or curviplanar zone composed of rocks that are more highly strained than the rocks adjacent to the fault zone
• Quartz starts to flow rather than fracture at about 300C
Semi-brittle shear zones
2004 Parkfield EarthquakeRamón Arrowsmith
& special guest Matt Fouch
Earthquake of the Month: Special Seminar
Brittle-ductile s.z.
Sense of shear
S-C fabric: S surface = schistosity, C surface = shear surfaces
Sense of shear
Sense of shear: Ductile shear zone
Pure vs. Simple shear
Pure vs. Simple shear
Analysis of shear strain
Continuous or discontinuous strain
Transpression or Transtension
Can have both pure and simple shear along a shear
zone
-R+AVelocities relative to stable North America