Welcome to Geophysics OASIS
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.
Instructor
A. FADIL, Geology Dept, FSSM-UCA, Marrakech, Morocco.
TextBook
Burger, R. E., Sheenean, A. F. and Jones, C. H., Introduction to Applied Geophysics: Exploring the Shallow Subsurface, W.W. Norton Company, New York / London, 2006.
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
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.
Seismic Refraction
We first examine seismic wave travel times in a homogeneous subsurface. Then we derive travel time and layer thickness expressions for a single subsurface interface, two horizontal interfaces, multiple horizontal interfaces, dipping interfaces, and "non-ideal" subsurface. Field data acquisition procedures and example applications of the refraction method are also covered.
Seismic Reflection
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
fr-pdf | en-pdf | fr-ppt
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.
