Applied Magnetics - Geology 495
Spring 2009
Professor: Steve Sheriff

Grading: Based on exams, problem sets, project reports, participation (on grading papers). The syllabus and the ad for the course provide some direction on content and your responsibilities.

 

Excel tips - Free Excel exercises	Magnetic & Gravity Lexicon
US magnetic data	Canadian magnetic data
Butler: Paleomagnetics ; Tauxe's Paleomag	NOAA Geomagnetism
USGS Potential Field Software (DOS, Oasis Montaj)	Equipment Setup & Use
Scientist's & Engineer's Digital Signal Processing	Handouts & Tips
Bibliography: Separation, Edge Detection, Depth

• 1/26/2009: Intro to course, general concepts - magnetic units, mine.
• 1/28: Geomagnetism, declination, inclination, Missoula (D, I, .xls), magnetic elements, geocentric axial dipole hypothesis, secular variation, magnetic potential, spherical coordinates, dv, and a Geomagnetic Field applet.
• 2/2: More on the equation for a uniformly magnetized sphere (Butler's appendix), the dipole equation a fundamental equation of paleomagnetism; inclination versus latitude.
• 2/4: Translations and rotations (1, 2, 3). Spherical trig (see Butler's appendix) and stereonet (web bonus: dot product) solutions for the distance between two points on a sphere, epicenter determination, apparent pole positions, and the calculation of apparent pole positions.
• 2/9: Problem set.  Pole to field mapping (D, I) <--> VGP, apparent polar wander (1), averaging vectors.
• 2/11: Class Cancelled.
• 2/16: President's day holiday
• 2/18: Flux around a dipole, buried dipole applet, and a start to rock magnetism: hysterisis (from Butler), Curie temperature, magnetic minerals, and domains (2).
• 2/23: Domains and grain sizes, classes of magnetic materials, magnetizations: NRM, TRM.
• 2/25: Auroras (Lorentz force, detector) , secondary magnetizations, VRM, vector mixing and magnetic cleaning by alternating field and thermal mechanisms, and the fold test for relative age of acquisition.
• 3/2: Hierarchical sampling (rocks, VGP, paleopoles); transforms (1, 2), 2D tectonics, relative velocity vectors.
• 3/5: Problem set(data.xls). More transform faults (Isacks_Oliver_Sykes), APW paths, Euler poles, hot spot tracks (1,2), hotspot reference frame, paleomagnetic Euler poles (figure).
• 3/9: Read this for self assessment then read a paleomagnetic paper of your interest for a short presentation/discussion wednesday; local paleomagnetic examples (Doughty, Jolly, Brunt, Sheriff).
• 3/11: Discuss Problem set (first guess), nonlinear and linear regression (2) and the papers you read.
• 3/16: Midterm Exam - equation sheet.
• 3/18: Magnetic prospecting; HRAM example Grauch & Hudson, 2007 (field, faults), inclination versus latitude, buried dipole (buried dipole data), local examples, magnetic anomalies vs latitude (1, 2, 3, 4), dipole applet. Total field (scalar) anomalies, fluxgate, proton precession (2) and cesium vapor magnetometers. Regional magnetic fields.
• 3/23: 2D modeling, Poisson's relation, Talwani algorithm, pblock, pdike.
• 3/25: Software: Magcad, Clausthal-applet; experimental design, sampling/resolution. Fourier series, transforms, and frequency filtering of potential fields; Fourier series applet, Fourier transform applet. Filters in the frequency domain - high pass, low pass, bandpass, notch, and threshold. 2D power/amplitude spectra, radial averages.
• 3/30 Spring Break
• 4/1: Spring Break
• 4/6: Filters in the frequency domain (DOS demo). Review convolution, seismic/radar example, upward continuation
• 4/8: Upward continuation & separation filtering, magnetics of a random layer (filters: depth, thickness), statistical methods (figures: sequence, spectrum) of separation (Spector & Grant Figure (1, 2)); upward continue some magnetic data (MYAP, LosP); Read this: Phillips, 1999(6 mb).
• 4/13: Decorrugation, matched filtering (example).
• 4/15: Gridding & contouring (figure: 4 methods) with Surfer; upward/downward continuation and matched filtering with USGS extensions to Oasis Montaj; magnetic data (MacKenzie Dikes, NW_MT, NC_MT, SW_MT). For these data (Canada, US), I already completed the longitude & latitude to UTM conversion using Corpscon.
  
  Assignment:
  
  • Make a new folder on the desktop, using your name or something distinct. Do all your downloads and calculations in this folder; it will end up with lots of files!
  • Choose one of the Montana data (NW_MT, NC_MT, SW_MT)) sets and use upward continuation to separate deeper sources from more shallow sources. Alternatively, choose an area in the US or Canada in which you are more interested. Download into your desktop folder.
  • For the same data set, use matched filtering to separate equivalent layers.
  • For the magnetic data from the MacKenzie dike swarm, see how well you can separate the signals from dikes versus that from deeper sources.
    
    Next Wednesday turn in a 3-5 page report carefully explaining your analysis and observations for the two data sets. Provide short accurate explanations of the steps you took, why you took them, and how they are pertinent to your results. I want to see that you understand what you are doing and are thinking about the results. Write it so that a Geoscience student, not in this class, could understand the highpoints. Remember that in Windows you can screen-grab figures of active windows using ALT-PrintScreen and paste them into Word.
    
    
• 4/20: Review (gridding, matched filtering: step-by-step); reduction to pole (RTP with latitude), pseudogravity.
• 4/22: Edge detection (disk); HGM, analytic signal (low latitudes), local wavenumber; then magnetic modeling using models from Surfer and PFmag3D (program) from R. Blakely in the USGS DOS  software collection. Read this for self assessment: Phillips, 1998 - it should be making sense.
  
  Assignment: Use Surfer, PFmag3D, & the USGS extensions in Oasis Montaj to investigate the horizontal gradient method, analytic signal, and local wavenumber edge detection routines on one of the simple models other than a disk. Next Wednesday turn in a 3-5 page report carefully explaining your analysis and observations for the two data sets (details as above).

• 4/27: More on matched layer choices. Depth estimates: slope half-slope (example), and Euler(2) deconvolution.
• 4/29: Edge detection examples (figure 1, 2); Euler deconvolution (figure 1, 2, low latitude) and depth estimates from the analytic signal method.
• 5/4: Depth estimates from the horizontal gradient method
• 5/6: Curvature/special function depth analysis - summary; Werner deconvolution. Take home exam.
• Finals Week - Final Exam - Monday 3:20

 

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