On the Spatial and Temporal Variations of Fault Damage and Related Properties
Abstract
The zone of damage surrounding faults is known to strongly alter their physical properties through earthquake cycles, such as the hydraulic diffusivity, the elastic properties and frictional strength. Consequently, fault damage zones influence the stress distribution, fluid flow, and rupture properties of faults. Damage zones have been observed and measured in a variety of ways, including reduced P and S wave velocity, increased attenuation, fault zone guided waves, altered drainage patterns, geodetic measurements across fault zones, and field observations of exhumed rocks over a range of outcrop scales. These observations give a wide range of constraints on the extent of damage zones that, on first inspection, are not easy to correlate. We provide a synoptic assessment of these observations that suggests that fault damage zones reach a maximum width of a few hundred metres at depth but can increase to several kilometres near the surface. The structure and physical properties of damage depends not only on fault maturity, but also on the scale of observation. The increase in damage zone width near the surface could be interpreted as an extensive homogeneous distribution of damage due to lower mean stress or a heterogenous distribution of smaller damage zones surrounding multiple fault cores that form flower structures at shallow depths. Measured at low resolution at the large scale, these two end members would appear similar and only observations at higher resolution on a smaller scale would resolve detail. The temporal evolution of damage zones depends on pressure and temperature (depth) and will involve asperity creep, material transport, and fluid influx leading to sealing and healing of different scale fracture networks on co- and postseismic timescales.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMMR32A..08F
- Keywords:
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- 1209 Tectonic deformation;
- GEODESY AND GRAVITY;
- 5104 Fracture and flow;
- PHYSICAL PROPERTIES OF ROCKS;
- 7209 Earthquake dynamics;
- SEISMOLOGY;
- 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICS