time dependent estimates of the velocity gradient tensor field for transient detection
DESCRIPTION
Time Dependent Estimates of the Velocity Gradient Tensor Field for Transient Detection. William Holt , Gina Shcherbenko, Eric Caruso, Yu Chen Acknowledgements: We thank SCEC for funding support. 0.1° x 0.1° Grid. Rigid Pacific Plate. - PowerPoint PPT PresentationTRANSCRIPT
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Time Dependent Estimates of the Velocity Gradient Tensor Field for Transient Detection
William Holt, Gina Shcherbenko, Eric Caruso, Yu Chen
Acknowledgements: We thank SCEC for funding support
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0.1° x 0.1° Grid
Rigid Pacific Plate
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Model magnitude of shear strain rates (pure SS style)(SCEC4.0 Velocity field)
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Smoothing or Damping• Maximize signal associated with GPS
• Achieve Reduced Chi-Squared misfit between model displacement and observed displacement of ~1.0 for all epochs
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χ = ( ˙ e ij )ij,kl
∑cells
∑T
Vij,kl−1( ˙ e kl )+ (vi − v i
obs )T Vi, j−1(v j − v j
obs )i, j
∑knots
∑
Haines, Jackson, Holt, Agnew [1998]
Beavan and Haines [2001]
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Time Series from SCEC IVc
WNRA – Phase 4c
4th order polynomial fit with annual and semi-annual terms
Annual and semi-annual removed
Red = 15 day moving average filter
Green = 4th order polynomial
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Output 2 week epoch solutions of displacement
2 Week Displacements
Subtract out ‘master solution’ to estimate signal only from transients
-For real data we used SCEC4.0 solution as a master solution-For other groups in the SCEC exercise we used time averaged solution (2007 – 2009).5 mm
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Output 2 week epoch solutions of displacement
2 Week Displacements
Subtract out ‘master solution’ to estimate signal only from transients
-For real data we used SCEC4.0 solution as a master solution-For other groups in the SCEC exercise we used time averaged solution (2007 – 2009).
Residual Displacements
Phase IVa5 mm 5 mm
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What Triggers Selection of Potential Transients?
• Accelerations
• Finite Strain
• Analysis of finite strain tensor and displacement vector fields
• Does signal look tectonic?
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d
dtδE( )
€
δE∫
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Phase IVa
Residual displacements reference solution subtracted out
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Finite Displacements + Strain (principal axes) Phase IVa
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Phase IVb
Residual displacements reference solution subtracted out
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Phase IVb Finite Displacements + Strain (principal axes)
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Phase IVc
Residual displacements reference solution subtracted out
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Finite Displacements + Finite Strain (Principal Axes) Phase IVc
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Summary of results from Phase IV• The modeling of displacements with
reference field removed captures spatial and temporal magnitudes of transients
• Method can be automated
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Analysis of PBO Data from 2010.35 – 2011.25• El Mayor-Cucapah post-seismic
motions and strains– Non-steady state motions with periods of
apparent increasing and decreasing strain
• High frequency strain changes in LA Basin region
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Finite Strain (Dilatations) + displacements: PBO Data 2010.35 – 2011.25
See poster B-143
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Residual displacements show rapid spatially correlated changes in LA region
2010.35