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Seismic Waves and Earthquake Location

Seismic Waves and Earthquake Location. Walter D. Mooney US Geological Survey California Mooney @ usgs.gov. Wave propagation animation. Seismogram showing different phases. SEISMIC WAVE VELOCITY. Body Waves. P-wave. Vp ~ √3 Vs. S-wave. Surface Waves.

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Seismic Waves and Earthquake Location

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  1. Seismic Waves and Earthquake Location Walter D. Mooney US Geological Survey California Mooney @ usgs.gov

  2. Wave propagation animation

  3. Seismogram showing different phases

  4. SEISMIC WAVE VELOCITY Body Waves P-wave Vp ~√3 Vs. S-wave Surface Waves Love Wave V S1 < VL< V S2 Rayleigh Wave VR < 0.92 VS

  5. Conversion of Seismic Phases at Rock Boundaries

  6. P* Pg Pn Seismogram showing converted phases

  7. Magnetic Tape Record Analog Record

  8. Analog Telemetric Film Record

  9. Major Discontinuities of the Earth

  10. Teleseismic Analog record

  11. Digital Record of the 2004 Sumatra Earthquake Mw 9.3

  12. T-phase of the Largest Aftershock of the 2004 Sumatra Earthquake Recorded at the VISK Station, India

  13. Travel Time Curves

  14. 1030 1430 1030 1430

  15. EARTHQUAKE LOCATION Manual Method for Location Computational Methods for Location Single-station Location Multi-station Location Computer Programs for Location HYPO 71 SEISAN

  16. Manual Method

  17. Computational Method P & S Arrival Data Station Coordinates Station Correction P-wave Velocity Model Vp/Vs Maximum Amplitude Signal Duration Input data: Computation : Geiger's (1912) method of least squares Technique Ri = i - t i

  18. STATION CORRECTION

  19. 3-Component Seismograms of an aftershock of the 2004 Sumatra Earthquake

  20. Wadati Plot Vp/Vs = 1.73

  21. Limitations in Precise Location: (b) Earthqauke occurs outside the Array Note: At least one S-phase is required to control the Hypocentre location (a) Earthquake occurs in a Circular Array

  22. Multiple Minima Problem

  23. EARTHQUAKE RELOCATION • Master Event Method • Average Residual Method • Homogeneous Station Method • Double-Difference (DD) Method • Joint Hypocentre Method rij = tij – (ij + Si)

  24. Tectonic Map of Northeast India Kayal et al., 2006

  25. Fault Plane Solutions of Earthquakes, Northeast India Kayal et al., 2006

  26. Pop Up Tectonics : Shillong Plateau Bilham & England, 2001 Kayal et al., 2006

  27. THANK YOU Fremantle, Perth

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