GEOL 483

What you are expected to know (for the exam):

General

• Strain, stress
• Hooke’s law
• Elastic potentials
• Characteristics of P, S, and Rayleigh waves
• Sampling interval, Nyquist frequency
• Dynamic range
• Fourier and Z-transforms (descriptive)
• Convolution, cross- and autocorrelation (descriptive)
• Application
• Relation to Fourier and Z-transform
• Requirements to a seismic source
• Generation of seismic waves
• by an explosion
• by a marine airgun source
• by a Vibroseis source (incl. Vibroseis correlation)
• Bubble effect/oscillations in marine sources
• Generation
• Elimination
• Principle of seismic detectors
• Electromagnetic geophone: damping, critical damping
• Rays and wavefronts
• Geometrical spreading
• Attenuation of seismic waves
• Surface waves

Refraction methods

• Snell's law, critical refraction, head waves
• Diving waves
• Ray parameter
• Apparent velocity and its application
• Travel-time and wavefront diagrams
• Critical distance, cross-over distance
• Time calculation in a 2-layer Earth (horizontal interfaces)
• Intercept time, delay time, reciprocal times
• Quantitative description of plus/minus and ABC techniques
• Generalized reciprocal Method
• Approximation of the dipping-layer case for small dip angles
• Elevation and weathering corrections for shot and receiver locations

Reflection method

• Physical basis of reflection method
• Wavelets
• Reflection and transmission, P/S mode conversions
• Boundary conditions for 1) contact of two solids and 2) free surface
• Reflectivity series
• Seismic trace as a convolution between the Earth’s response and source wavelet
• Wave potentials
• Zero-offset sections
• Pre-stack and post-stack imaging
• Acoustic impedance, acoustic impedance contrast
• Zoeppritz equations and Scattering matrix
• Amplitude Variations with Offset and Angle (AVO and AVA)
• Fresnel zone, horizontal and vertical resolution
• Multiples
• Calculation of reflection time from a single horizontal interface
• Velocities: average, instantaneous, interval, root mean square (RMS), stacking
• Use of RMS velocity, time-average equation
• Moveout time, normal moveout calculation, dynamic correction
• Shot gathers, inner and outer traces, receiver gathers
• CMP binning and gathers, CMP fold
• Ground roll and its suppression in the field and during processing
• Airwave and its suppression
• Dipping layer case. Difference of shot and CMP orders in the case of dip
• Dip moveout
• Frequency and moveout filtering
• Deconvolution
• Processing overview
• Principles of VSP
• Migration - plane reflector and point diffractor cases

Tomography and Location

• Principle of generalized linear inverse
• Least-squares inverse
• Damped and weighted inverse
• Resulution  matrix and checkerboard resolution tests
• Forward and inverse travel-time problem
• Principle of velocity tomography
• Principle of seismic source location

 Formula sheet