A Geophysical Study: Desert Hot Springs, CA Electric and Electromagnetic Response of the Mission Creek Fault Undergraduate research project: Brad Coffey, Ben Drenth, Amber Harris, Shannon Kobs, Mellisa Le, Doug Moore

Introduction Purpose Location Geology Methods

Purpose Use of electrical and electromagnetic geophysical methods to assess the properties of the Mission Creek Fault and determine the usefulness of these methods in similar areas.

Location

Aerial Photo

Geology

Geophysical Methods Electrical Resistivity Electromagnetic Very Low Frequency (VLF) VLF – resistivity (VLF-R) Horizontal Loop Electromagnetics (HLEM)

Resistivity Previous Work Location Methods Results Interpretation Multielectrode Resistivity 2002

Locations of soundings taken by Chad Lukkarila and Dr. Diehl

Resistivity methods Schlumberger Arrays 250 meter maximum spacing Originally interpreted using Resist3 New interpretation using Zhody program

Resistivity Cross-section Line

Zhody Layered Model Results N-NES-SW

Multielectrode Resistivity

Electromagnetics Very Low Frequency (VLF) VLF-Resistivity Horizontal Loop EM (HLEM)

VLF and VLF-R S R P Hy Ez Ex

VLF VLF tilt-angle response Horizontal Conductor

VLF

VLF-R N-NES-SW

HLEM

HLEM Field Data

HLEM Models

Model Summary Resistive Overburden Fault Plane Water Table S-SWN-NE m

Conclusions Successful identification of fault location through electrical and electromagnetic methods Future Work: Resistive or conductive fault gouge Interaction of fault and groundwater

Acknowledgements Thanks to Dr. Alex Mayer for his informative talk on the hydrogeology of the Desert Hot Springs Area. A special thanks to Dr. Young for arranging the field trip, leading us in the interpretation of the data, and feeding us at that awesome steak place.

References ________, Emix-mm User’s Manual, Interpex Limited, Golden, Colorado, USA. Karous, M., and S. E. Hjelt (1983) Linear Filtering of VLF Dip-Angle measurements, Geophysical Prospecting, 31: Lukkarila, Chad R., 1999, Refinement of a groundwater flow model: Upper Coachella Valley, Riverside County, California, MS Thesis, Department of Geological Engineering and Sciences, Michigan Technological University McNeil, J.D “Advances in Electromagnetic Methods for Groundwater Studies.” SAGEEP 1988, Proctor, R. J Geology of the Desert Hot Springs-Upper Coachella Valley Area, California. Special Report 94 California Division of Mines and Geology, San Fransisco, 50 p. Reynolds, J. M An Introduction to Applied and Environmental Geophysics. John Wiley & Sons, Inc. New York.

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Photos – Miscellaneous

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Photos – Miscellaneous