1 Kinematics of Kinematics of Transrotational Tectonism Transrotational Tectonism in the California Transverse Ranges and in the California Transverse Ranges and Its Contribution to Cumulative Slip Along Its Contribution to Cumulative Slip Along the San Andreas Transform Fault System the San Andreas Transform Fault System William Dickinson William Dickinson 20 April 2004 20 April 2004 Wrench Tectonics - Different End Wrench Tectonics - Different End Members Members (Sylvester, 1988)
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Kinematics of Kinematics of Transrotational TectonismTransrotational Tectonismin the California Transverse Ranges andin the California Transverse Ranges andIts Contribution to Cumulative Slip AlongIts Contribution to Cumulative Slip Alongthe San Andreas Transform Fault Systemthe San Andreas Transform Fault System
William DickinsonWilliam Dickinson
20 April 200420 April 2004
Wrench Tectonics - Different EndWrench Tectonics - Different EndMembersMembers
(Sylvester, 1988)
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San Andreas Slip DeficitSan Andreas Slip Deficit
Total Transform Slip in Central California:Total Transform Slip in Central California:~48 mm/yr~48 mm/yr
Average Slip Rate on SAF: ~35 mm/yrAverage Slip Rate on SAF: ~35 mm/yr
Average Shear on ECSZ: ~8-12 mm/yrAverage Shear on ECSZ: ~8-12 mm/yr
Total Deficit: <5 mm/yrTotal Deficit: <5 mm/yr
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Conceptual ModelConceptual Model
Initial State (tInitial State (t00))
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Constant-Width Model (tConstant-Width Model (t11))
Constant-Width Model (tConstant-Width Model (t22))
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Initial State (tInitial State (t00))
"Pinned" Model (t"Pinned" Model (t11))
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"Pinned" Model (t"Pinned" Model (t22))
Initial State (tInitial State (t00))
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"Decoupled" Model (t"Decoupled" Model (t11))
"Decoupled" Model (t"Decoupled" Model (t22))
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DynamicsDynamics
Two Models:Two Models:1.1. Side-DrivenSide-Driven
•• Requires attachment of rotating panels to shearRequires attachment of rotating panels to shearzone sides (and bottom detachment)zone sides (and bottom detachment)
2.2. Bottom-DrivenBottom-Driven•• Requires attachment of rotating panels to shearingRequires attachment of rotating panels to shearing
mantle lithosphere (and side detachment)mantle lithosphere (and side detachment)
Both could drive the "Pinned" orBoth could drive the "Pinned" or"Decoupled" models"Decoupled" models
Rotation has been roughly constant at 5.7-5.9Rotation has been roughly constant at 5.7-5.9˚̊for the last ~15 Mafor the last ~15 Ma
Two Possibilities:Two Possibilities:1.1. Different rotation rates for each domain, but rotationDifferent rotation rates for each domain, but rotation
for the same amount of timefor the same amount of time
2.2. Equal rotation rates for each domain, but differentEqual rotation rates for each domain, but differenttimingtiming
The latter is preferred, and implies that theThe latter is preferred, and implies that thelength of the rotating panels shortens with timelength of the rotating panels shortens with time