1. Magnetotelluric Interpretation of La Bajada Canyon Jeremy Gunter SDSU SAGE 2004

2. Topics of Investigation  Brief Overview of MT  Instrumentation  Study Area  1D and 2D Interpretations  Implication of Interpretation

3. 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

4. Instrumentation Geometrics Stratagem EH4  Provides 2D MT data  Frequency: 10hz to 92k Hz, Controlled Source  Capability for Natural Source MT

5. Study Area  La Bajada Fault Zone on Cochiti Pueblo Land

6. 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

7. La Bajada Soundings

9. La Bajada’s 1D World

10. La Bajada’s 1D World…

11. 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?

12. La Bajada in 2D

13. Profile of 2D Inversion

14. 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