Mike's Deck Flashcards by mike w

Stress has how many components?

And what type are they / how many of each are there?

9 components
3 Normal
6 Shear

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In 3D shear Strain, how many components does the top surface has?

Two

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what is the symmetry in the stress and strain mapped to?

To the Stiffness Tensor

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VIA Symmetry reduces 81 variables to how many?

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under standard practice, reduce the 9 components into how many unique components?

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6x6 gives a _____ _____ (matrix) of 36

a stiffness tensor

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The matrix for isotropic media has how many parameters and what are they?

two.
Lamda
Mew

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How independent parameters are there in a transverse isotropic media

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what is poisson’s ratio numbers for cork and rubber?

Cork = 0.0
Rubber = 0.5

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what six parameters contribute to the derivation of the wave equation?

longitudinal
element length
movement
extension
strain
stress
Hook's Law

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What are the big two that lead to the wave equation?

Hooks Law and Newton’s second law

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frequency = ?

1 / T (tao) where T is period

slide 14 / 51 from L5

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what does the convolution integral compute?

One output sample

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**End of Review **

End of Review

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what will an event in a medium usually create?

Wavelet

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what do repeated events create?

Repeated wavelets

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What’s special about the wavelet that an earthquake creates?

the wavelet will propagate in different modes

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How can a wavelet become a seismic trace??

by taking different paths

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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

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what are the two assumptions made with wavelets?

Superposition and Addition

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What is the superposition assumption?

the content of one wavelet does no interfere with another wavelet; they pass each other

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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