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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. 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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**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**Model magnitude of shear strain rates (pure SS**style)(SCEC4.0 Velocity field)**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]**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**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**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**What Triggers Selection of Potential Transients?**• Accelerations • Finite Strain • Analysis of finite strain tensor and displacement vector fields • Does signal look tectonic?**Phase IVa**Residual displacements reference solution subtracted out**Phase IVb**Residual displacements reference solution subtracted out**Phase IVc**Residual displacements reference solution subtracted out**Finite Displacements + Finite Strain (Principal Axes)**Phase IVc**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**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**Finite Strain (Dilatations) + displacements: PBO Data**2010.35 – 2011.25 See poster B-143**Residual displacements show rapid spatially correlated**changes in LA region 2010.35

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