Burger:
Exploration Geophysics of teh Shallow Subsurface.
Learning Objectives
Provide the students a good back-ground on geophysical instruments (AD converters, seismometers) and on their field operation. Provide a robust theoretical background to applyed geophysics, focusing particularly on seismic refraction and seismic reflection methods. Provide the studends a robust back-ground on seismic data analysis.
Prerequisites
Mathematics and physics. Integral and differential calculus.
Teaching Methods
Lectures.
Type of Assessment
Oral exam.
Course program
Relation between the seismic source, the medium and the recorded siesmogram.
Strain: strain tensor, shear and normal strain, cubic dilatation.
Stress: stress tensor, shear and normal stress, hydrostatic pressure, stress and strain relation, elastic moduli (Young modulus, bulk modulus, Poisson ratio, Rigidity, Lamée constants).
Relationships between elastic moduli and seismic velocities.
Huygens principle, ray and wavefront relation, plane and spherical wavefronts.
Snell law for p and s waves as a function of takeoff angle. Seismic wave attenuation, geometrical spreading, anelastic attenuation, quality factor, Zoeppritz coefficients.
Seismometry. A/D conversion. Time series (sampling rate, Nyquist frequency) Aliasing. Decibel.
Frourier analysis, DFT, FFT, IDFT, IFFT. Convolution. Theorem of discrete convolution. Filtering. Cross and auto-correlation functions.
Seismic refraction: travel time for direct and refracted waves. Seismic wave velocity from travel time. Critical distance. Cross-over distance. Travel time from multiple discontinuities. Travel time from an inclined discontinuity. Low velocity layer, hidden layer, lateral variation of seismic velocity, hidden topography. Delay times method.
Seismic reflection. Travel time for reflected waves at a horizontal interface. Travel time for reflected waves at an inclined horizontal interface. t2/x2. Funzione. Normal Move Out. Deep Move Put. Dix equation.