Time Dependent Estimates of the Velocity Gradient Tensor Field for Transient Detection
This study presents a detailed analysis of the velocity gradient tensor field, aimed at transient detection in the Pacific Plate region. By utilizing a refined grid model and applying smoothing techniques, we maximize the GPS signal while achieving a reduced Chi-Squared misfit for observed and modeled displacements. Through a systematic approach, we explore finite strain and acceleration metrics to identify potential transient events. Our results illustrate the effective modeling of displacements, capturing significant spatial and temporal transient magnitudes.
Time Dependent Estimates of the Velocity Gradient Tensor Field for Transient Detection
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Presentation Transcript
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
