GEOL 4850 - Introduction to Applied Geophysics

• Analyze common midpoint reflection data in terms of an irregular contact.
• Analyze walkaway reflection data in terms of dipping, planar contacts.
• Be able to convert between SI units of acceleration and the geophysical units milliGal and the gravitational unit (gu).
• Be able to correct gravity data for the effects of latitude, elevation (Bouguer), terrain, tides and instrument drift to obtain a gravity anomaly.
• Be able to correct magnetic data for horizontal and vertical variation as well as for diurnal effects.
• Be able to derive the the basic 4-electrode equation relating current, potential difference, resistivity and electrode position and its specific forms for the Wenner, Schlumberger and dipole-dipole arrays..
• Be able to describe the data processing flow of common depth point reflection analysis.
• Be able to describe the extension of 2D common depth point imaging to 3D.
• Be able to explain induced magnetization as a source of magnetic anomalies.
• Be able to explain the principles underlying frequency-domain electromagnetic methods including VLF and Slingram techniques.
• Be able to explain the concept of apparent resistivity and its variation with electrode spacing.
• Be able to explain the concept of non-uniqueness in gravity interpretation.
• Be able to explain the concept of resistivity equivalence.
• Be able to interpret gravity anomalies in terms of subsurface density variations using simple geometric formulas and inversion software.
• Be able to interpret ground-penetrating radar reflection and diffraction data in terms of the depths of reflecting contacts and of buried objects.
• Be able to interpret magnetic anomalies in terms of subsurface susceptibility variations using simple geometric formulas and inversion software.
• Be able to qualitatively interpret data from both a constant-spread and an expanding-spread array.
• Be able to select an appropriate combination of geophysical methods for characterizing a given subsurface target.
• Invert expanding-spread apparent resistivity data using inversion software to obtain resistivities and thicknesses of subsurface layers.
• Know how to set up a field system for acquiring seismic reflection data in walkaway, roll along and common midpoint modes.
• Know the concept of normal moveout and its relation to velocity and reflector depth.
• Know the fundamental physics governing electrical resistivity and the general range of resistivities for different lithologies.
• Know the fundamental physics governing seismic wave propagation and the general range of seismic velocities for different lithologies.
• Know the general ranges of densities for various lithologies.
• Understand Newton’s law of gravitation as applied to the Earth and the variation of acceleration with latitude.
• Understand how to acquire basic seismic refraction data in the field and to analyze and interpret it in terms of dipping, planar contacts.
• Understand the concept of an apparent resistivity pseudosection and its relation to a resistivity image obtained from dipole-dipole data.
• Understand the concepts of migration and static corrections.
• Understand the effect of conductivity, frequency and contrasts in dielectric constant on reflected radar amplitudes.
• Understand the effects of profile strike with respect to declination and inclination on the pattern of magnetic anomalies.
• Understand the ranges of magnetic susceptibilities for various lithologies and the role of iron.
• Understand the relationship between RMS and interval seismic velocities.
• Understand the relationship between ground-penetrating radar velocity and subsurface dielectric constant.
• Understand the relationships between skin-depth, effective depth, subsurface conductivity and electromagnetic frequency.
• Understand the trade-off bertween resolution (frequency) and radar depth of penetration.
• Understand the variation of the geomagnetic field’s total intensity, declination and inclination over the Earth’s surface.