Detailed Aeromagnetic Studies

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Detailed Aeromagnetic Studies

• Fault Interpretations from High-Resolution
  Aeromagnetic Data
• V.J.S. Tien Grauch
• U. S. Geological Survey

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NORTHERN ALBUQUERQUE BASIN
Grauch, 1999
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Outline

• Survey specifications
• What aeromagnetic data show
• Enhancements for showing faults
• Interpreted faults vs. mapped faults
• A range-front fault interpretation
• Conclusions
• Future work

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Aeromagnetic Survey Specifications

• Helicopter Survey
• NW-SE flight lines, spaced 200 m apart
• NE-SW tie lines, spaced 1000 m apart
• Average height of magnetometer 120 m
• Total line km 5740
• Total area 940 km2

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Dixie Valley Aeromagnetic Data
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References Smith, 1968 Hudson and Geissman,
1987, 1991 Hudson et al., 1999
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Dixie Valley Aeromagnetic Data
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Separation of Aeromagnetic Data into Components
short-wavelength component (shallow sources)
medium-wavelength component
long-wavelength component (deep sources)
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Horizontal-gradient method for gravity data
Cordell, 1979
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Horizontal-gradient method for magnetic data
Cordell and Grauch, 1985
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HGM of short- wavelength component of
pseudogravity
Shallow Fault Enhancement
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HGM of short- wavelength component of
pseudogravity
Shallow Fault Enhancement with Mapped Faults
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HGM of Fault Model
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HGM of Deep vs. Shallow Fault Model
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Shallow Fault Enhancement with Interpreted Faults
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Interpreted and Mapped Faults
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HGM of Dipping Fault Model
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NW
Profile Across Apparent Bench
SE
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Conclusions

• High-resolution aeromagnetic data show
• Bedrock patterns
• Range-front faults
• Intra-basin fault patterns
• Intra-basin faults correspond well to mapped
  faults
• Aeromagnetic data suggest steeply dipping
  range-front fault with benches

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Suggested Future Magnetic Work

• Profile models
• Focus on range front and geothermal areas
• Combine with other information
• Better determine magnetic rock properties
• Follow-up ground magnetics
• Compare magnetic signatures to alteration, faults
  with springs, etc.
• Additional flying in Dixie Valley

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Dixie Valley Aeromagnetic Data with
InterpretedFaults