1. Name: Introduction to Applied Geophysics - ERTH/PHYS 2270.01

2. Calendar Description

An introduction to using physical principles to explore the Earth’s subsurface, with an emphasis on near-surface applications. Topics will include seismic, gravity, magnetic, electrical, and electromagnetic surveying techniques, and their application in prospecting, hydrogeology, environmental assessments, and well-logging. The geophysics field school, normally conducted during the last week of April, is an integral part of this class.

3. Prerequisites: First year physics and mathematics.

4. Instructor: Mladen Nedimović

Life Sciences Centre Room 3054, Phone: 494-4524, e-mail: mladen@dal.ca

5. Textbook:

Burger, Robert, E., Sheenean, Anne F. and Jones, Craig, H.,
Introduction to Applied Geophysics; Exploring the Shallow Subsurface,
W. W. Norton Company, New York/London, 2006

6. Class Components:

Lectures: 2 x 75 minutes each week (T,W: 17:35 - 18:50)
Tutorials 2 x 1 hour each week (T,W: 19:00 – 20:00)
Field work 3 days in late April after final exams

7. Assessment:

The final grade of the class will be based on the following;

Assignments (5) 40%
Mid-term 25%
Final Examination (during last class) 25%
Field work (immediately after exam period) 10%

8. Grade conversion:

Numerical results will be converted to letter grades as follows:

A     89.9-85
A-    84.9-80

B+   79.9-75
B     74.9-70
B-    69.9-65

C+   64.9-62
C     61.9-58
C-    57.9-55

D     54.9-50
F      49.9-0

9. Class Outline:

Introduction. The class starts with a brief intro to geophysics and geophysical techniques, with emphasis on the methods that will be covered in the class. Also introduced are concepts of geophysical data acquisition, data processing, and data and image interpretation.

Seismic wave fundamentals. Presented is fundamental information on seismic waves, wave propagation, ray paths in layered media, wave attenuation and amplitude, and energy sources and seismic recording equipment. Basic knowledge of this material is required for understanding both seismic refraction and reflection methods of exploration.

Refraction method. We first examine seismic wave traveltimes in a homogeneous subsurface. Then we derive traveltime and layer thickness expressions for a single subsurface interface, two horizontal interfaces, multiple horizontal interfaces, dipping interfaces, and "nonideal" subsurface. Field data acquisition procedures and example applications of the refraction method are also covered.

Reflection method. Similar to the refraction method, we work our way from simpler subsurface geometry (single horizontal interface) to more complex subsurface geometries (e.g., multiple horizontal interfaces, dipping interface). Then we study data collection procedures and computer processing of reflection data, and finish the reflection method by analyzing field examples.

Electrical resistivity. This section starts with a brief introduction into to the basic electricity. We then look into electrical currents in a homogeneous isotropic earth, and earth with one horizontal interface, multiple horizontal interfaces, one vertical contact, two vertical contacts, and dipping interfaces. This is followed by a study of field data collection procedures, quantitative interpretation of apparent resistivity curves, and example applications of electrical resistivity surveying. A brief tour through other electrical methods is also presented.

Gravity. We start with fundamental relationships, measuring gravity, reductions to measured field data, and basic field procedures required during surveying. A study of gravity effects of simple geometric shapes, gravity anomaly analysis, and gravity interpretation follows. Example applications of the gravity method are also covered.

Magnetics. In this section, we start with fundamental relationships and then move on to study characteristics of the Earth's magnetic field, instrumentation used to measure this field, and magnetic field surveying. We follow with a review of magnetic effects of simple geometric shapes, interpretation of magnetic data, and examples of magnetic method application.

Electromagnetics. In the final segment of this class we introduce electromagnetic (EM) waves, EM sounding, EM field techniques, ground-penetrating radar, and examples of applications of electromagnetic surveying.

10. Assignments:

Target for the number of assignment is five. Each assignment, except the first, will be focused on one of the major geophysical methods studied in the class. Problems sets will be based on the class textbook and will require the use software that accompanies the class textbook.

11. Computer Usage:

Students will use their personal computers to solve computational problems handed out as part of their assignments. Students are encouraged to bring their laptop computers to tutorials where similar problems will be examined. The software used for data analysis is located on a CD that accompanies the class textbook "Introduction to Applied Geophysics". On this CD there is a total of five programs available: REFRACT for refraction seismology, REFLECT for reflection seismology, RESIST for electrical resistivity, GRAVMAG for gravity and magnetics, and DIFFRACT for ground-penetrating radar. The CD also contains a number of data tables in Microsoft Excel format. All of the software modules are designed to run on both Macintosh and Windows systems, can perform forward and inverse modeling, and support all the major exploration methods covered in the book.

12. Tutorials/Labs:

Tutorials are devoted to learning how to solve various numerical problems and how to use the software.
This is also ideal time for students to ask various questions regarding the class.

13. Field School:

Field school immediately after examinations is an integral part of the class. Students are divided into groups, which rotate through all of the techniques during three to four days.  Evenings are spent working up results.

14. Further Geophysics Classes:

ERTH/PHYS 3270: The Solid Earth
An introduction to global geophysics, including the workings of both the Earth’s surface (and its deep interior.  Starting from plate tectonics, this class will explore the Earth as a unified dynamic system.  The class will include topics such as seismology, earthquakes, mantle convection, crustal accretion, isostacy,and  the Earth’s magnetic field.  There will be discussions of radioactivity and the Earth’s heat budget, since these are essential to our understanding of our planet.

Format: lecture 3 hours, tutorial 2 hours
Prerequisite: ERTH/PHYS 2270

ERTH/OCEA 4470/5470: Introduction to Seismic Imaging

This class teaches the basic techniques of the reflection seismic method for imaging of earth structures [such as used in hydrocarbon exploration]. Class lectures will introduce concepts and techniques that will be applied in computer lab to the processing of a multi-channel seismic dataset. Concepts covered will include: source and receiver geometry, digital filtering, deconvolution, velocity analysis, stacking, and migration.

Format: lecture/lab 1/3 hours
Prerequisite: ERTH/PHYS 2270 or instructor's consent

ERTH/OCEA 4480/5480: Advanced Seismic Imaging
This class teaches more advanced techniques of seismic imaging of earth structures. Class lectures will introduce techniques that will be applied in the computer lab to the processing of multi-channel reflection and wide-angle refraction seismic datasets. Concepts covered will include: multiple removal, pre-stack migration in time and depth, amplitude analysis, velocity modeling and inversion, and seismic attributes.

Format: lecture/lab 1/3 hours
Prerequisite: ERTH/PHYS 2270,  ERTH 4470/5470, or instructor's consent