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The brittle and ductile strength of the San Andreas fault system, California

Carena, Sara, and Christoph Moder (2009), The brittle and ductile strength of the San Andreas fault system, California, in AGU Fall Meeting 2009, pp. C4+.

Abstract
The strength of major strike-slip faults like the San Andreas has been controversial for decades. We use a global finite-element code with a variable-resolution grid and global plate-driving forces to determine whether the effective friction on the San Andreas fault is high (0.6 - 1), intermediate (0.3 - 0.5) or low (≤ 0.2), whether a single value of effective friction can be used for all mapped active faults within California, and whether weakening of the ductile lower crust associated with faulting is important. We compare our model results with existing data on fault slip-rates, GPS velocities, stress field, and earthquakes depth distribution. The comparison indicates that all faults are weak (effective friction ≤ 0.2), and that additional weakening of the major faults in the network is important (i.e. brittle strength is variable among faults). The effective friction for the strongest faults in the region is in the range 0.2 - 0.05. The San Andreas fault is a very weak fault among weak faults, with effective friction < 0.05 for most of its length. All viable solutions also indicate that weakening of the lower crust below major faults in the system is necessary, i.e. major faults must exist as discrete, narrow shear zones in the lower crust as well, while minor faults could be limited to the brittle crust. Comparison between observed slip-rates and slip-rates calculated for several models. Model 2 is our best model. Model 3 is the strong-faults case: all fault slip-rates are reduced to as little as 5% - 10% of their observed values. μ* = effective friction, ucw = linear slip-dependent weakening in upper crust, lcw = weakening in lower crust, SAF = San Andreas fault, SJF = San Jacinto fault.
Further information
BibTeX
@inproceedings{id1673,
  author = {Sara Carena and Christoph Moder},
  booktitle = {AGU Fall Meeting 2009},
  month = {dec},
  pages = {C4+},
  title = {{The brittle and ductile strength of the San Andreas fault system, California}},
  year = {2009},
  url = {http://adsabs.harvard.edu/abs/2009AGUFM.T12C..04C},
}
EndNote
%A Carena, Sara
%A Moder, Christoph
%D 2009
%P C4+
%T The brittle and ductile strength of the San Andreas fault system, California
%U http://adsabs.harvard.edu/abs/2009AGUFM.T12C..04C
%8 dec
%B AGU Fall Meeting 2009
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Printed 22. Jan 2020 11:25