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Magnetotelluric Interpretation of La Bajada
Canyon
Magnetotelluric Interpretation of La Bajada
Canyon
Jeremy Gunter
SDSU
SAGE 2004
Topics of InvestigationTopics of Investigation
Brief Overview of MT Instrumentation Study Area 1D and 2D Interpretations Implication of Interpretation
What is Magnetotellurics?
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
InstrumentationInstrumentationGeometrics Stratagem EH4
Provides 2D MT data Frequency: 10hz to 92k Hz, Controlled Source Capability for Natural Source MT
Study AreaStudy Area La Bajada Fault Zone on Cochiti Pueblo Land
1D Interpretation1D 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
Τ≅ ρδ 5.0
m*100Ω=ρm*5Ω=ρ m353≅δ
km58.1≅δ
La Bajada SoundingsLa Bajada Soundings
La Bajada SoundingsLa Bajada Soundings
La Bajada’s 1D WorldLa Bajada’s 1D World
La Bajada’s 1D World…La Bajada’s 1D World…
Analysis of 1D DataAnalysis of 1D Data 2 to 3 Major Resolvable Layers
Line 100 to ~400 = R,C,RLine 500 to 800 = Small R, Large C
Resistivity Change from ~100 ohm-m to ~10 ohm-m What could this mean?
La Bajada in 2DLa Bajada in 2D
Profile of 2D InversionProfile of 2D Inversion
Implications and Improvements
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
