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Processing Issues for Near Source Strong Motion Recordings

Explore the effects of significant near-fault ground motion, rupture directivity, and fling (tectonic displacement) in strong motion recordings. Learn about various processing methods, baseline corrections, and spectral acceleration analysis.

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Processing Issues for Near Source Strong Motion Recordings

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  1. Processing Issues for Near Source Strong Motion Recordings Robert Graves URS Group, Inc. • Significant Near Fault Ground Motion Effects • Rupture Directivity • Fling (tectonic displacement) Project Sponsors: PG&E, PEER-Lifelines / NGA COSMOS Strong Motion Record Processing

  2. COSMOS Strong Motion Record Processing

  3. Fling Effects: Fault parallel velocity can be large very close to strike slip fault COSMOS Strong Motion Record Processing

  4. Fling Effects: Asymmetric footwall / hanging wall motions very close to reverse faults COSMOS Strong Motion Record Processing

  5. Recordings with Significant Fling • Sparse Sampling • R < 5 km • Mw ~ 7.5 • Different distance and frequency behavior from “generic” ground motions COSMOS Strong Motion Record Processing

  6. Baseline Correction • Graizer (1979) • Iwan et al. (1985) • Boore (2001) Choice of t1 and t2 is non-unique Boore (2001) COSMOS Strong Motion Record Processing

  7. Although the results look physically plausible, the residual displacements can be sensitive to t1, t2Quadratic fit to velocity gives best fit to GPS residual displacementin this case Boore (2001) COSMOS Strong Motion Record Processing

  8. Tokachi Oki: 1 Hz GPS / SM Records Clinton (2004) COSMOS Strong Motion Record Processing

  9. Waveform sensitivity to baseline correction parameters t1: acc > 50 cm/sec2 (Iwan) t2(1): Boore’s v0 t2(2): acc < 50 cm/sec2 (Iwan) t2(3): 2 x t2(2) – t1 COSMOS Strong Motion Record Processing

  10. Spectral Acceleration is fairly insensitive to t1, t2 COSMOS Strong Motion Record Processing

  11. Ground Velocity is somewhat sensitive to t1, t2 COSMOS Strong Motion Record Processing

  12. COSMOS Strong Motion Record Processing

  13. Fling adjusted motions can be quite sensitive to t1, t2 COSMOS Strong Motion Record Processing

  14. CONCLUSIONS COSMOS Strong Motion Record Processing

  15. COSMOS Strong Motion Record Processing

  16. t1: acc > 50 cm/sec2 (Iwan) t2(1): Boore’s v0 t2(2): acc < 50 cm/sec2 (Iwan) t2(3): 2 x t2(2) – t1 COSMOS Strong Motion Record Processing

  17. Boore (2001) COSMOS Strong Motion Record Processing

  18. COSMOS Strong Motion Record Processing

  19. COSMOS Strong Motion Record Processing

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