1 / 27

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. .

frederique
Download Presentation

GEOL 414 Applied Geophysics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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.

  2. 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. Applied Geophysics

  3. 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

  4. American Geological Institute IndexGeology Disciplines • Geology • Economic Geology • Geochemistry • Geophysics • Paleontology • Hydrology • Soil Science • Engineering Geology • Oceanography • Planetology

  5. American Geological Institute IndexSub-disciplines in Geophysics • General Geophysics • Experimental Geophysics • Exploration Geophysics • Geodesy • Geomagnetism & paleomagnetism • Gravity • Heat Flow • Seismology • Marine Geophysics

  6. American Geological Institute IndexSub-disciplines in Geophysics • Extraterrestrial Geophysics* • Soil Physics* • Mathematical Geology* • Mineral Physics* • Stable Isotopes*

  7. 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

  8. Topics in some Geophysics Textbooks: Applied GeophysicsTelford, 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

  9. Applied and Environmental GeophysicsReynolds • Potential Field Methods • Applied Seismology • Electrical Methods • Electromagnetic Methods

  10. 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

  11. 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

  12. 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

  13. 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

  14. Seismology • Measured units – time & distance • Interpreted units – velocity • Application interpretation – rock type, structure • Refraction • Reflection • Earthquakes The Wave Equation

  15. Resistivity • Units – ohm m • V = iR • R = rA/L • Various arrays with characteristic electrode spacing

  16. Bouguer Gravity of the Lake St. Martin Impact Structure

  17. Residual Gravity of the Lake St. Martin Impact Structure

  18. Surprise Valley, California

  19. Surprise Valley, California

  20. Surprise Valley, California Digital elevation model

  21. Surprise Valley, California Bouguer Gravity contours Red lines are seismic lines Black lines are gravity profiles seen in next two slides

  22. Surprise Valley, California

  23. Surprise Valley, California Surprise Valley, California Bouguer gravity profiles

  24. Surprise Valley, California Vertical derivative of the Bouguer gravity profiles

  25. The Geoid

  26. Gravity at UND • The predicted gravity is given in units of 'milligals': 1 gal = 1 cm sec-21 kilogal = 1000 gal 1 milligal = 1/1000 gal Latitude: 47.91877432 • Longitude: 97.06790622 • MSL Height: 252.9 • Predicted gravity: 980798 +/- 2 milligals

More Related