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.
-
- 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).
Geosciences Department - The University of Montana - 32 Campus Drive #1296 - Missoula, MT 59812-1296
Phone: (406) 243-2341 Fax: (406) 243-4028 Email: geology@mso.umt.edu

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