Mike's Deck Flashcards
Stress has how many components?
And what type are they / how many of each are there?
9 components
3 Normal
6 Shear
In 3D shear Strain, how many components does the top surface has?
Two
what is the symmetry in the stress and strain mapped to?
To the Stiffness Tensor
VIA Symmetry reduces 81 variables to how many?
21
under standard practice, reduce the 9 components into how many unique components?
6
6x6 gives a _____ _____ (matrix) of 36
a stiffness tensor
The matrix for isotropic media has how many parameters and what are they?
two.
Lamda
Mew
How independent parameters are there in a transverse isotropic media
5
what is poisson’s ratio numbers for cork and rubber?
Cork = 0.0 Rubber = 0.5
what six parameters contribute to the derivation of the wave equation?
longitudinal element length movement extension strain stress Hook's Law
What are the big two that lead to the wave equation?
Hooks Law and Newton’s second law
frequency = ?
1 / T (tao) where T is period
slide 14 / 51 from L5
what does the convolution integral compute?
One output sample
**End of Review **
End of Review
what will an event in a medium usually create?
Wavelet
what do repeated events create?
Repeated wavelets
What’s special about the wavelet that an earthquake creates?
the wavelet will propagate in different modes
How can a wavelet become a seismic trace??
by taking different paths
What are the three different paths that a wavelet can take when they become a seismic trace?
Through the Earth
from different reflecting surfaces
from additional excitations
what are the two assumptions made with wavelets?
Superposition and Addition
What is the superposition assumption?
the content of one wavelet does no interfere with another wavelet; they pass each other
What is the addition assumption?
The amplitudes add
what are the five types of wavelets?
slide 20 / 51 , L5
Casual minimum phase mixed phase max phase zero phase
what three factors are associated with seismic reflection trace?
Different rock types
The reflection coefficient
Convolve with a wavelet
How do the three factors for a seismic trace mathematically equate to becoming a Seismic trace?
Reflectivity (different Rock type) * Wavelet + Noise = Seismic Trace
Does data with a higher frequency have a lower or higher resolution?
Higher
what are some examples of frequencies?
Voice - pitch… hi low
Musical Instrument - harmonics
What is a Fourier Transform
A periodic waveform composed of sinusoids
slides 28 - 34 L5
See them for more details
filter design is possible in what domain?
Frequency domain
Filter design is not possible in what domain?
Time domain
As t or f tend to zero, what happens? (discrete Fourier Transform (FT) tends to a _____ FT)
discrete FT tends to a continuous FT
where is the origin in a 2D FT? (fourier Transform)
in the center
slide 45 / 51 L5
Take a peak
what is spectral whitening also known as?
Deconvolution
What is deconvolution?
filtering process which removes a wavelet from the recorded seismic trace by reversing the process of convolution.
With deconvolution, what are three ways to get the inverse of the wavelet??
Least Squares
Z Transform
Fourier Transform
What is the fourier transform theory?
Fourier’s theory states that a given signal can be synthesized as a summation of sinusoidal waves of various amplitudes, frequencies and phases.
Using the Fourier Transform a ____ domain signal is transformed to the _____ domain where it is equivalent to an Amplitude Spectrum and a Phase Spectrum.
Using the Fourier Transform a time domain signal is transformed to the frequency domain where it is equivalent to an Amplitude Spectrum and a Phase Spectrum.
What is convolution?
mathematical way of combining two signals to achieve a third, modified signal.
Convolution in the ____ domain is represented in the _____ domain by multiplying the amplitude spectra and adding the phase spectra.
Convolution in the time domain is represented in the frequency domain by a multiplying the amplitude spectra and adding the phase spectra.
why is convolution and deconvolution used?
In principal by deconvolving the source wavelet we could obtain the earth’s reflectivity
Is noise in a signal wanted or not wanted
Not wanted
Is it essential to use deconvolution after migration?
Yes , slide 50 / 51 L5
Sampling Data theory states that the sample rate, Fsamp, must be at least _____ of Fmax
Twice
Fsamp > 2Fmax
in the sampling theory, what must you be able to sample?
The highest frequency in the data, Fmax
May have to high the cut the sample data.
Ex) Slide 8 / 69 of L6
if Fsamp = 500hz, what does dt =?
0.002sec
Fsamp = 1 / dt
Aliasing : when ___
E(f) f > Fmax
As t or f tend to ____; ____FT tends to a _____ FT
zero
discrete
continuous
A periodic waveform is composed of what?
Sinusoids
after correlation, of a vibrator sweep, is the line flat or or not?
it becomes flat
is it okay to have no zeros in W(f)?
Yes it is Ok to have a smooth W(f) with no zeros Wsm(f)
slide 17 / 69 L6
