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Time Dependent Estimates of the Velocity Gradient Tensor Field for Transient Detection

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.

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Time Dependent Estimates of the Velocity Gradient Tensor Field for Transient Detection

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  1. 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

  2. 0.1° x 0.1° Grid Rigid Pacific Plate

  3. Model magnitude of shear strain rates (pure SS style)(SCEC4.0 Velocity field)

  4. 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 Haines, Jackson, Holt, Agnew [1998] Beavan and Haines [2001]

  5. Time Series from SCEC IVc Red = 15 day moving average filter 4th order polynomial fit with annual and semi-annual terms Annual and semi-annual removed Green = 4th order polynomial WNRA – Phase 4c

  6. Output 2 week epoch solutions of displacement 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 2 Week Displacements

  7. Output 2 week epoch solutions of displacement 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). Phase IVa 5 mm 5 mm 2 Week Displacements Residual Displacements

  8. What Triggers Selection of Potential Transients? • Accelerations • Finite Strain • Analysis of finite strain tensor and displacement vector fields • Does signal look tectonic?

  9. Phase IVa Residual displacements  reference solution subtracted out

  10. Finite Displacements + Strain (principal axes) Phase IVa

  11. Phase IVb Residual displacements  reference solution subtracted out

  12. Phase IVb Finite Displacements + Strain (principal axes)

  13. Phase IVc Residual displacements  reference solution subtracted out

  14. Finite Displacements + Finite Strain (Principal Axes) Phase IVc

  15. 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

  16. 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

  17. Finite Strain (Dilatations) + displacements: PBO Data 2010.35 – 2011.25 See poster B-143

  18. Residual displacements show rapid spatially correlated changes in LA region 2010.35

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