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-NE
S-SW
Multielectrode Resistivity
Electromagnetics
Very Low Frequency (VLF)
VLF-Resistivity
Horizontal Loop EM (HLEM)
VLF and VLF-R
S
R
P
Ez
Ex
Hy
VLF
VLF tilt-angle response
Horizontal Conductor
VLF
VLF-R
VLF-R Field Data
80
70
500
60
400
50
300
40
30
200
20
100
10
0
0
40
80
120
160
200
240
280
Phase Angle (Degrees)
Apparent Resistivity
(ohm*m)
600
apparent
resistivity
(ohm*m)
phase
angle
(degrees)
0
320
Location (m)
N-NE
S-SW
HLEM
HLEM Field Data
HLEM Models
HLEM - Line 2
Layer 1 & 2 Emixmm Model Depths
Distance (m)
250
0
300
350
400
450
500
550
600
-20
-40
-80
-100
-120
HLEM - Line 3
Layer 1 Emixmm Model Depths
-140
Distance (m)
-160
0
-20
-40
-60
Depth (m)
Depth (m)
-60
-80
-100
-120
-140
-160
0
50
100
150
200
250
300
350
400
450
500
550
600
Model Summary
N-NE
S-SW
Resistive Overburden
Water Table
Fault Plane
30-50 m
Water Table
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
________, 1988. 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: 782-794.
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. 1988 “Advances in Electromagnetic Methods for
Groundwater Studies.” SAGEEP 1988, 252-348.
Proctor, R. J. 1968. 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. 1997. An Introduction to Applied and Environmental
Geophysics. John Wiley & Sons, Inc. New York.
Questions?
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