Imaging Crustal and Mantle Geology With Scattered Waves

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Imaging Crustal and Mantle Geology With Scattered
Waves

• Justin Revenaugh
• Earth Sciences/CSIDE/IGPP
• University of Santa Cruz

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Acknowledgements

• Colin Reasoner (SAIC)
• Andrew Frederiksen (UCSC)

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What are scattered waves?

• Scattered waves originate through the interaction
  of primary (and scattered) waves with
  heterogeneities. They do not exist in a
  homogenous medium.

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An Example of Seismic Scattering Precursors to
PKP
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Precursors to PKP
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Seismic Coda
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Why Study Scattered Waves?

• Ignoring them doesnt make them go away
• Scattered waves can image geologic
  contactstravel time tomography cannot
• Sensitive to cracksuseful for understanding
  stress variability
• Necessary to separate earthquake source and
  propagation-induced waveform complexity

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Tomography vs Scattered-Wave Imaging
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Migration Schematic
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Scattered-Wave Travel Times Part 1
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Scattered-Wave Travel Times Part 2
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Teleseismic Event Distribution
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Processing Flowchart
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Source Deconvolution
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Processing Flowchart
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Migration Schematic
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Processing Flowchart
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Bootstrapping for Scattering Potential
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P to P Scattering in the Mantle
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P to P Scattering in the Mantle
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P to P Scattering in the Mantle
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P to P Scattering in the Mantle
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P to P Scattering in the Mantle
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Synthetic P to P Scattering in the Mantle
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A Model for Mantle Scattering
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Conclusions

• Subcrustal lithosphere subduction beneath the
  Transverse Ranges is the dominant source of upper
  mantle scattering in Southern California.
• May imply through-going breaks in the lithosphere
  matching breaks in the Ranges.
• There are no big surprises lurking beneath
  Southern California.

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Resolution and Variance Tests
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Aligned Seismograms
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Scattering and Seismicity
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Faulting Statistics
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Seismicity Statistics
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Seismicity Distribution Part 1
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Seismicity Distribution Part 2
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Landers Region
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Along-Fault Averaging Scheme
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Along-Fault Scattering and Seismicity Variations
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Along-Fault Scattering and Slip Variation
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San Jacinto Fault Zone
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San Jacinto Scattering Resolution
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San Jacinto Scattering Variance Tests
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San Jacinto Regional Scattering
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Along-Fault Scattering and Seismicity Variations
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Transverse Ranges Scattering
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Along-Fault Scattering and Seismicity Variations
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Transverse Ranges Seismicity
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Central California Faults
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San Andreas Segmentation
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San Andreas Offset Estimation
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Realigned San Andreas Profiles
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San Andreas Segmentation
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San Andreas Segmentation
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San Jacinto Regional Scattering
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San Jacinto Offset Estimation
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Realigned San Jacinto Profiles
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San Jacinto Aligned Scattering
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Perturbed Fault Zones
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Perturbed SJFZ Results
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Conclusions

• Scattered-wave imaging with teleseismic P works.
• Crustal scattering is pattern predictive of
  seismicity and co-seismic slip
• A large portion of the scattering heterogeneity
  translates coherently with the fault
• Pre-fault structure exerts a significant
  influence on seismogenesis

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Conclusions

• Results can be used to assess seismic hazard
• Pinpoint areas of greatest slip
• Recognize regions of seismic deficit
• Method has potential applications in hydrogeology
• Crack detection, fracture density mapping
• Passive or active mode