Seismic Waves

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Seismic Waves and Earthquake Location
Walter D. Mooney US Geological Survey California M
ooney _at_ usgs.gov
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Wave propagation animation
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Seismogram showing different phases
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SEISMIC WAVE VELOCITY
Body Waves
P-wave
Vp v3 Vs.
S-wave
Surface Waves
Love Wave V S1 lt VLlt V S2
Rayleigh Wave VR lt 0.92 VS
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Conversion of Seismic Phases at Rock Boundaries
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Seismogram showing converted phases
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Magnetic Tape Record
Analog Record
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Analog Telemetric Film Record
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Major Discontinuities of the Earth
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Teleseismic Analog record
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Digital Record of the 2004 Sumatra Earthquake Mw
9.3
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T-phase of the Largest Aftershock of the 2004
Sumatra Earthquake Recorded at the VISK Station,
India
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Travel Time Curves
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(No Transcript)
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EARTHQUAKE LOCATION
Manual Method for Location
Computational Methods for Location
Single-station Location
Multi-station Location
Computer Programs for Location
HYPO 71
SEISAN
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Manual Method
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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
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STATION CORRECTION
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3-Component Seismograms of an aftershock of the
2004 Sumatra Earthquake
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Wadati Plot
Vp/Vs 1.73
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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
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Multiple Minima Problem
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EARTHQUAKE RELOCATION

• Master Event Method

• Average Residual Method

• Homogeneous Station Method

• Double-Difference (DD) Method

• Joint Hypocentre Method

rij tij (?ij Si)
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Tectonic Map of Northeast India
Kayal et al., 2006
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Fault Plane Solutions of Earthquakes, Northeast
India
Kayal et al., 2006
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Pop Up Tectonics Shillong Plateau
Bilham England, 2001
Kayal et al., 2006
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THANK YOU
Fremantle, Perth