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Magnetotelluric Interpretation of La Bajada Canyon. Jeremy Gunter SDSU SAGE 2004. Topics of Investigation. Brief Overview of MT Instrumentation Study Area 1D and 2D Interpretations Implication of Interpretation. What is Magnetotellurics?.
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Magnetotelluric Interpretation of La Bajada Canyon Jeremy Gunter SDSU SAGE 2004
Topics of Investigation • Brief Overview of MT • Instrumentation • Study Area • 1D and 2D Interpretations • Implication of Interpretation
What is Magnetotellurics? • MT = The Study of Naturally Occurring E and H Fields at Surface of Earth to Map the Subsurface • Assumption of Normally Incident Plane Wave • Sources: Solar Winds, Lightning Discharge, and Active Sources
Instrumentation Geometrics Stratagem EH4 • Provides 2D MT data • Frequency: 10hz to 92k Hz, Controlled Source • Capability for Natural Source MT
Study Area • La Bajada Fault Zone on Cochiti Pueblo Land
1D Interpretation • Force 3D World into 1D Model • Implications = Earth is a Heterogeneous Half-Space • Layered Homogeneous Half-Space Allows for Skin Depth: • Depth of Investigation = then if then at 10hz or T=0.1 for Homogeneous Half-Space
Analysis of 1D Data • 2 to 3 Major Resolvable Layers • Line 100 to ~400 = R,C,R • Line 500 to 800 = Small R, Large C • Resistivity Change from ~100 ohm-m to ~10 ohm-m • What could this mean?
Implications and Improvements • Successful Location of La Bajada Fault, and Possibly Another Fault??? • Layer Determination, and Water Table Interface • More MT Stations to the West • Use Lower Frequencies