GEOL 414 Applied Geophysics : GEOL 414 Applied Geophysics Fall Semester 2006
Principles of various geophysical methods and their application to geologic problems. Prerequisites: Geology 101, Mathematics 213, Physics 204 or 206. 3 credits.
Applied Geophysics : Applied Geophysics
Textbook: Burger, Sheehan, and Jones, Introduction to Applied Geophysics, 2006, W.W. Norton & Co. Inc., ISBN 0393-92637-0
Course Goals: To give students an understanding of the physical principles of geophysical methods so that they will appreciate the strengths and limitations of the methods. After certain fundamentals have been mastered, the students study the procedures used in data acquisition and use the department's equipment to conduct geophysical surveys. The final phase of each section of the course gives students training in interpretation of geophysical data.
Geol 414 Topic Sequence : Geol 414 Topic Sequence Section 1 Introduction to Geophysics -Methods, Units, Applications, Geophysical Societies, Geophysical literature
Section 2 Gravity fundamentals
Gravity surveying
Gravity data reduction and analysis
Section 3 Magnetic fundamentals
Magnetic surveying
Magnetic data reduction and analysis
Section 4 Combined gravity and magnetic survey field project
Section 5 Electrical Methods and Surveying
Section 6 Seismology fundamentals
Section 7 Refraction seismology
Section 8 Reflection seismology
Section 9 Thermal methods
American Geological Institute Index Geology Disciplines : American Geological Institute Index Geology Disciplines Geology
Economic Geology
Geochemistry
Geophysics
Paleontology
Hydrology
Soil Science
Engineering Geology
Oceanography
Planetology
American Geological Institute Index Sub-disciplines in Geophysics : American Geological Institute Index Sub-disciplines in Geophysics General Geophysics
Experimental Geophysics
Exploration Geophysics
Geodesy
Geomagnetism & paleomagnetism
Gravity
Heat Flow
Seismology
Marine Geophysics
American Geological Institute Index Sub-disciplines in Geophysics : American Geological Institute Index Sub-disciplines in Geophysics Extraterrestrial Geophysics*
Soil Physics*
Mathematical Geology*
Mineral Physics*
Stable Isotopes*
American Geophysical Union Sections : American Geophysical Union Sections Atmospheric Sciences
Biogeosciences
Geodesy
Geomagnetism and Paleomagnetism
Hydrology
Ocean Sciences
Planetary Sciences
Seismology
Space Physics and Aeronomy
Tectonophysics
Volcanology, Geochemistry, and Petrology
Topics in some Geophysics Textbooks: Applied Geophysics Telford, Geldart, Sheriff : Topics in some Geophysics Textbooks: Applied Geophysics Telford, Geldart, Sheriff Gravity Methods
Magnetic Methods
Seismic Methods
Electrical Properties of Rocks and Minerals
Natural Electrical Sources
Electromagnetic Methods
Resistivity Method
Induced Polarization
Radioactivity Method
Geophysical Well Logging
Applied and Environmental Geophysics Reynolds : Applied and Environmental Geophysics Reynolds Potential Field Methods
Applied Seismology
Electrical Methods
Electromagnetic Methods
Gravity : Gravity Units - gals 1 gal = 1 cm s-2
Absolute gravity
Relative gravity
Range 983164 to 978049 mgals
Property of Earth – density distribution
F = Gmm r-2
g = Gm r-2
Heat Flow : Heat Flow Units – mW m-2
Q = ΛΚ
Q = Q0 + Ab
A = A0 e-z/b
Range 103 to 0
Mean ~ 84 mW m-2
Laplace’s equation Poisson’s equation The diffusion equation
Magnetics : Magnetics Units – nanoTeslas nT
7 measurable components
Declination
Inclination
F (total field)
X (north)
Y (east)
Z (vertical)
H (horizontal)
Coulomb’s Law Field Strength Magnetic Intensity
Magnetics : Magnetics Units – nanoTeslas nT
Main field 60,000 to 30,000 nT
Core dynamo
External field 10’s nT
Diurnal, seasonal, ionization of atmosphere solar wind currents, storms
Anomalous field 1000’s nT
Magnetic susceptibility of crust
Seismology : Seismology Measured units – time & distance
Interpreted units – velocity
Application interpretation – rock type, structure
Refraction
Reflection
Earthquakes
The Wave Equation
Resistivity : Resistivity Units – ohm m
V = iR
R = rA/L
Various arrays with characteristic electrode spacing
Slide16 : Bouguer Gravity of the Lake St. Martin Impact Structure
Slide17 : Residual Gravity of the Lake St. Martin Impact Structure
Slide18 : Surprise Valley, California
Slide19 : Surprise Valley, California
Slide20 : Surprise Valley, California
Digital elevation model
Slide21 : Surprise Valley, California
Bouguer Gravity contours
Red lines are seismic lines
Black lines are gravity profiles seen in next two slides
Slide23 : Surprise Valley, California
Slide24 : Surprise Valley, California Surprise Valley, California
Bouguer gravity profiles
Slide25 : Surprise Valley, California
Vertical derivative of the Bouguer gravity profiles
Slide26 : The Geoid
Gravity at UND : Gravity at UND The predicted gravity is given in units of 'milligals': 1 gal = 1 cm sec-2 1 kilogal = 1000 gal 1 milligal = 1/1000 gal Latitude: 47.91877432
Longitude: 97.06790622
MSL Height: 252.9
Predicted gravity: 980798 +/- 2 milligals