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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. High frequency seismometers Streckeisen STS-2 Guralp CMG-3T Teledyne GS-13

  9. Vault of an observatory

  10. IDA MK8 DAS Another popular model

  11. Major Discontinuities of the Earth

  12. Teleseismic Analog record

  13. Digital Record of the 2004 Sumatra Earthquake Mw 9.3

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

  15. Travel Time Curves

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

  17. Manual Method

  18. Seismogram

  19. 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

  20. STATION CORRECTION

  21. 3-Component Seismograms of an aftershock of the 2004 Sumatra Earthquake

  22. Wadati Plot Vp/Vs = 1.73

  23. 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

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

  25. THANK YOU Fremantle, Perth

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