Lecturers:
Dr Steve Hearn
Dr Peter Furness

Course Summary:
This elementary course introduces the main techniques used in exploration geophysics. Basic theory on seismic, electrical, magnetic and gravity methods is covered, incorporating instrumentation, data processing and interpretation techniques. Practical classes are used to illustrate geophysical applications to real and synthetic data. A field excursion provides exposure to representative geophysical equipment and field practices.

Contact:
5 contact hours per week

Lecture Room:
First year laboratory - Steele Building

Assumed Background:
Basic mathematics (approximately Level 1) including basic algebra, calculus and trigonometry. Introductory geology and physics are recommended but not essential. Contact Dr. Hearn for further details.

Assessment:
Final Examination 85%, Field Trip 10%, Other Practical Work 5%

Field Trip: Long weekend in May. Cost: approximately $120 (including food, campsite, transport)

Course Outline:

Gravity and Seismic Methods (Dr Steve Hearn)

The Gravity Method - Basic Theory
Newton's Law of Universal Gravitation; gravitation acceleration and potential; units of acceleration; calculation of acceleration due to finite masses; concepts of density contrast and gravity anomalies; analytic and numerical approaches.

The Gravity Method - Instrumentation
Sensitivity requirements for gravity measurements; stable and unstable gravity meters; the zero-length spring; examples – Worden, and Lacoste & Romberg meters.

The Gravity Method - Practical Aspects
Land survey techniques; drift adjustment; reduction of gravity data to Bouguer Anomalies; qualitative and quantitative approaches to interpretation.

Basic Concepts of the Exploration Seismic Method
P and S waves; surface waves (Love and Rayleigh); seismic velocity; acoustic impedance; Snell's Law; wavefronts; ray paths; reflection and transmission coefficients; practical examples of different lithologies; elastic constants.

Seismic Refraction - Basic Theory
Physical basis of refraction; head waves; critical angle; ray paths and travel time equation for simple plane horizontal layer model; extension of travel time equations to multiple layers; ambiguities arising from dipping layers.

Seismic Refraction - Reciprocal Method Interpretation
Reversed refraction shooting; calculation of the time-depth; physical significance of time-depth; time-depth to depth conversion; velocity analyses techniques; generalised reciprocal method.

Seismic Refraction - Logistics
Refraction instrumentation; sources; shooting patterns; data processing; applications of refraction.

Seismic Reflection - Theory
Geometry of reflection; travel-time equations; normal moveout (NMO); reflection coefficients revisited; CMP stacking.

Seismic Reflection - Logistics
CMP acquisition techniques; reflection sources; geophones; recording instruments; fundamentals of reflection data processing.

Seismic Reflection - Interpretation
Example reflection records; seismic sections; appearance of faulting and folding; applications in petroleum, coal, engineering and crustal studies.

Practicals
* Integrated gravity & magnetic interpretation of igneous intrusion
* Reduction of raw gravity measurements to Bouguer Anomalies
* Geophysical and spectral image processing
* Seismic refraction interpretation - Intercept Method
* Seismic refraction interpretation - Reciprocal Method
* Seismic reflection interpretation
* Interpretation of Field Trip Data

Magnetic and Electrical Methods (Dr Peter Furness)

Magnetic Method - Basic Theory
Overview; units; Coulomb's Law; magnetic field; scalar potential; superposition.

Magnetic Properties of Rocks
Magnetic dipole; magnetisation; induced magnetic properties; remnant magnetisation.

Magnetic Method - Field Measurements
The geomagnetic field; proton precession magnetometer; field procedures.

Electrical Properties of Rocks
Resistivity; conduction processes; conduction in rocks.

Resistivity Method - Basic Theory
Overview; point electrode potentials; 3D current flow; Ohm's Law; apparent resistivity.

Resistivity Method - Field Techniques
Electrode arrays; field procedure.

Resistivity Method - Applications
Resistivity sounding; resistivity profiling.

Induced Polarisation Method
Experimental observations in time and frequency domains; electrode polarisation; membrane polarisation; field techniques; data presentation; interpretation.

Spontaneous Polarisation Method
Overview; electrochemical causation; field procedure; data presentation; interpretation.

Electromagnetic Method - Basic Theory
Sinusoidal functions; Biot Savart Law; Faraday's Law of Induction; mutual inductance; induced currents in continuous conductors.

Electromagnetic Method - Continuous Wave Systems
Overview; conductive loop analysis; response function; response parameter; Slingram System; flux linkage diagrams; Turam System; flux linkage analysis; interpretation; Argand Diagrams.

Electromagnetic Method - Transient Systems
Overview; basic principles; conductive loop analysis; interpretation.

Geophysical Case Histories

Practicals
* Magnetic interpretation
* Resistivity interpretation
* Interpretation of mineralised SPs
* Induced polarisation interpretation
* Interpretation of Slingram EM data
* Interpretation of Field Trip Data

ERTH3020 Assessment Procedures:

Typical Assessment breakdown is: Mid-Semester Exam 40% Final Exam 40% Field trip and report 10%, Other practical work 10%.

Examination material and practical work is assessed on the technical accuracy of submitted work, scientific logic, and presentation. Field work assessment is based primarily on a submitted report (approximately 5-10 pages) incorporating summary of the data acquisition and analysis techniques used, geophysical interpretation, and recommendations for future work. The field performance of the student will also be considered. Further details on assessment procedures are provided prior to each assessable task.

Except where group work is specified, all work must be that of the author. Departmental policy on non-compliance with assessment procedures can be obtained from the Department of Earth Sciences office in the Steele Building.