Gravity and Electromagnetics - Geology 438
Professor: Steve Sheriff
Grading: Based on exams, problem sets, project reports, participation
Spring 2006 - Syllabus
The Summer of Applied Geophysical Experience (Los Alamos National Lab)
The Society of Exploration Geophysics scholarships

• 1/23/06: Problems, Mass, moment, gravity (Newton, Maskelyne), and mantle/core
• 1/25/06: Richter's clock problem, spherical coordinates, more on mass, moment, and density with depth, Press' Monte Carlo approach, equatorial bulge.
• 1/30: Chauvenet's principle, moment-mass problem, the Earth-Moon system, tidal friction, lunar recession (4.4 +/-0.6 cm/yr),
• 2/1: International Gravity Formula (gth), the geoid (NGS, PNW, US, world geoid), Free Air and Simple Bouguer Corrections
• 2/6: Matrix solutions (1, 2), linear density with depth, terrain corrections
• 2/8: Terrain density, density from FAA, the buried sphere, 2 spheres, interpreting Bouguer anomalies, ambiguity and uniqueness, topography & anomalies, case study: Nyack
• 2/13: Regional-residual Problem, Bouguer anomalies: Missoula Valley, Northern Rockies, US, regional demo, Missoula Valley(ppt), NE Missoula Valley (Hennes ppt)
• 2/15: Minnesota (1,2), salt dome, Gauss' theorem, Talwani algorithm, 2D modeling with GravCadW, Swan Valley iterative method
• 2/20: Presidents (dead) day
• 2/22: Regional-residual .dat, Drift corrections, self assessment: USGS example, Airy and Pratt (isostacy).
• 2/27: mountain roots, accomodation space, sedimentary basins (2), P. Birds insights into the regional tectonics of Montana, Crustal thickness (NA, world, histograms), uplift following erosion, Elev/BA profile
• 3/1: Landscape and erosion, fault scarp erosion, Hudson's Bay (geoid)
• 3/6: Basic GPS, differential GPS, GPS error (1, 2, 3, 4), PDOP figure, operating the CG3, measuring table height.
• 3/8: Operating the GPS unit, more gravity measurements
• 3/13: Problem for today - process and interpret our measurements, gravity flow chart, and gravity assignment.
• 3/15: Midterm Exam on material through 3/8.
• 3/20: Flexure of the crust & lithosphere (A.Watt's), Flexure from a periodic load (here's the mathcad document) continued
• 3/22: elastic thickness from FAA analysis, flexural response function
• 3/27: Spring Break
• 3/29: Spring Break
• 4/3: Flexure from line loads (mcad doc), foreland basins, Purcell Anticlinorium-Sweetgrass Arch system.
• 4/5: Gravity modeling problems, flexure - numerical solution (Li et al.); Numerical solution from an ice load- NW MT: overall, dip, deformation, deformed contour, GPS-terraces. Self assessment! Animation
• 4/10: Resistivity (applet, Wenner, Schlumberger, dipole-dipole, compare 'em), values, methods, case studies: water(2), barrier island, landfill, karst, clay, channel, software (Sounder, Res2Dinv)
• 4/12: Resistivity in the field at the Riverbowl Field (Syscal switch); switch method for psuedosections
• 4/17: We'll look at your simple Bouguer anomalies, then download & invert resistivity data; Self assessment: resistivity depths, and methods
• 4/19: Field day.
• 4/24: GPR introduction, EM waves, GPR applet, moveout, GPR images (1, 2, 3), Noel's moraine, 2-way travel time, synthetic reflections (Excel version), read the case studies from Mala and Sensors & Software
• 4/26: As a group, take the Syscal resistivity equipment to the field (your choice of venue), structure an experiment that will show something, then collect comparative Wenner and Dipole-Dipole data. Process and interpret those data and give me a joint presentation on the experiment and the results.
• 51: Electric results in the classroom and radar basics and equipment
• 5/3: GPR in the field.
• 5/10 - Gravity presentations and Final (3:20-5:20).

Here's what happened in Spring 2005:

Last Year - Spring 2004:

• 1/26/04: Problems, mass, moment, gravity - much of it in spherical coordinates, (Newton, Maskelyne, Hutton, Huygens)
• 1/28: Problems for next Wednesday, more on density with depth, core-mantle, and the Earth-Moon system.
• 2/2: Richer's pendulum, equatorial bulge, tidal friction, lunar recession (4.4 +/-0.6 cm/yr)
• 2/4: Problem 2; International Gravity Formula (gth), and the geoid (NGS, PNW, US, world geoid), Free Air and Simple Bouguer Corrections.
• 2/9: Terrain corrections, terrain density, density from FAA, Bouguer anomalies (Missoula Valley, Northern Rockies, US), and the buried sphere (lunar orbits applet, 3-body.exe (DOS))
• 2/11: Problems (data), 2 spheres, interpreting Bouguer anomalies, ambiguity and uniqueness, case study-Evans, 1999, Missoula Valley(ppt)
• 2/16: President's Day
• 2/18: Regional demo & practice, Gauss' theorem, Minnesota (1,2), the Nyack project (ppt)
• 2/23: Discuss anomaly separation, NE Missoula Valley (Hennes ppt), Talwani algorithm, 2D modeling with GravCadW, Swan Valley iterative method
• 2/25: A problem, regional-residual practice, USGS example, topography & anomalies, Airy and Pratt (isostacy),
• 3/2: Drift corrections, - Jeremy's data: base stations, measuring relative gravity, correcting to known gravity, FAA, sBA
• 3/4: Terrain corrections (Demo, How to), FAA Basin & Range, what's not Airy supported?, mountain roots, accomodation space, sedimentary basins (2)
• 3/8: P. Birds insights into the regional tectonics of Montana, Crustal thickness (NA, world, histograms), uplift following erosion, Elev/BA profile
• 3/10: Landscape and erosion, fault scarp erosion, Hudson's Bay (geoid),
• 3/15: Problems, sedimentary basin depths, mantle viscosity, backstripping, Elastic thickness
• 3/17: Puget Sound rebound & tilt, flexure of the crust & lithosphere (A.Watt's)
• 3/22: Flexure from a periodic load (here's the mathcad document) continued; elastic thickness from FAA analysis, flexural response function
• 3/24: Time in the bank for field work!
• 4/5: flexure from line loads (mcad doc), foreland basins, Purcell Anticlinorium-Sweetgrass Arch system
• 4/7: Basic GPS, differential GPS, GPS error (1, 2, 3, 4), PDOP figure, operating the GPS unit
• 4/12: Differentially correcting our measurements, gravity flow chart, operating the CG3, measuring furniture heights, and gravity assignment
• 4/14: Field day - time for your gravity projects; no class.
• 4/19: Ground Penetrating Radar, GPR demo (250 MHz, shielded antenna) and operation
• 4/21: Field day - time for your gravity projects; no class.
• 4/26: GPR near the football stadium. Read the case studies from Mala and Sensors & Software
• 4/28: EM waves, GPR applet, GPR images (1, 2, 3), resistivity?
• 5/3: GSA Meeting - go to geophysics talks or work on projects
• 5/5: GSA Meeting - go to geophysics talks or work on projects
• 5/12: Our last meeting is 3:10 - 5:20; because it is FINALS WEEK!

Previous Exams

Case Studies

Equipment & Procedures:

Read the Gravimeter's Scale	Calculate Drift Corrections	Gravity Flow Chart
Terrain Corrections	GravcadW	PRO-XRS GPS (from Trimble)

 

Earth Coordinate Systems	Geodetic Datums	NGS Geoid Page
GPS Overview	SEG Virtual Museum	Wolfram Resources
Representative textbooks	Society of Environmental and Engineering Geophysics	AGU Reviews of Environmental Geophysics
Environmental Geophysics at Columbia University	Keele University, UK	Boise State - CGISS
Case Studies	Berkely Course Applied Geophysics

• The Summer of Applied Geophysical Experience supported by Los Alamos National Lab and the Department of Energy.
• The SEG (Society of Exploration Geophysicists) scholarship program.

• Exercise one covers relative versus absolute addresses and graphing equations.
• Exercise two introduces Excel's array functions for transposing, multiplying and inverting matrices.
• Exercise three uses the array functions for solving simultaneous equations and fitting lines to linear data.
• Exercise four demonstrates Excel's LINEST() function for least squares.
• Exercise five requires importing ASCII data, sorting, MEDIAN(), and AVERAGE.