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GeoPhysics > Mike's Deck > Flashcards

Mike's Deck Flashcards

1
Q

Stress has how many components?

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

A

9 components
3 Normal
6 Shear

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2
Q

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

A

Two

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3
Q

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

A

To the Stiffness Tensor

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4
Q

VIA Symmetry reduces 81 variables to how many?

A

21

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5
Q

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

A

6

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6
Q

6x6 gives a _____ _____ (matrix) of 36

A

a stiffness tensor

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7
Q

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

A

two.
Lamda
Mew

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8
Q

How independent parameters are there in a transverse isotropic media

A

5

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9
Q

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

A 
Cork = 0.0
Rubber = 0.5
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10
Q

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

A 
longitudinal
element length
movement
extension
strain
stress
Hook's Law
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11
Q

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

A

Hooks Law and Newton’s second law

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12
Q

frequency = ?

A

1 / T (tao) where T is period

slide 14 / 51 from L5

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13
Q

what does the convolution integral compute?

A

One output sample

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14
Q

**End of Review **

A

End of Review

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15
Q

what will an event in a medium usually create?

A

Wavelet

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16
Q

what do repeated events create?

A

Repeated wavelets

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17
Q

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

A

the wavelet will propagate in different modes

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18
Q

How can a wavelet become a seismic trace??

A

by taking different paths

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19
Q

What are the three different paths that a wavelet can take when they become a seismic trace?

A

Through the Earth
from different reflecting surfaces
from additional excitations

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20
Q

what are the two assumptions made with wavelets?

A

Superposition and Addition

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21
Q

What is the superposition assumption?

A

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

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22
Q

What is the addition assumption?

A

The amplitudes add

23
Q

what are the five types of wavelets?

slide 20 / 51 , L5

A 
Casual
minimum phase
mixed phase
max phase
zero phase
24
Q

what three factors are associated with seismic reflection trace?

A

Different rock types
The reflection coefficient
Convolve with a wavelet

25
Q

How do the three factors for a seismic trace mathematically equate to becoming a Seismic trace?

A

Reflectivity (different Rock type) * Wavelet + Noise = Seismic Trace

26
Q

Does data with a higher frequency have a lower or higher resolution?

A

Higher

27
Q

what are some examples of frequencies?

A

Voice - pitch… hi low

Musical Instrument - harmonics

28
Q

What is a Fourier Transform

A

A periodic waveform composed of sinusoids

29
Q

slides 28 - 34 L5

A

See them for more details

30
Q

filter design is possible in what domain?

A

Frequency domain

31
Q

Filter design is not possible in what domain?

A

Time domain

32
Q

As t or f tend to zero, what happens? (discrete Fourier Transform (FT) tends to a _____ FT)

A

discrete FT tends to a continuous FT

33
Q

where is the origin in a 2D FT? (fourier Transform)

A

in the center

34
Q

slide 45 / 51 L5

A

Take a peak

35
Q

what is spectral whitening also known as?

A

Deconvolution

36
Q

What is deconvolution?

A

filtering process which removes a wavelet from the recorded seismic trace by reversing the process of convolution.

37
Q

With deconvolution, what are three ways to get the inverse of the wavelet??

A

Least Squares
Z Transform
Fourier Transform

38
Q

What is the fourier transform theory?

A

Fourier’s theory states that a given signal can be synthesized as a summation of sinusoidal waves of various amplitudes, frequencies and phases.

39
Q

Using the Fourier Transform a ____ domain signal is transformed to the _____ domain where it is equivalent to an Amplitude Spectrum and a Phase Spectrum.

A

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.

40
Q

What is convolution?

A

mathematical way of combining two signals to achieve a third, modified signal.

41
Q

Convolution in the ____ domain is represented in the _____ domain by multiplying the amplitude spectra and adding the phase spectra.

A

Convolution in the time domain is represented in the frequency domain by a multiplying the amplitude spectra and adding the phase spectra.

42
Q

why is convolution and deconvolution used?

A

In principal by deconvolving the source wavelet we could obtain the earth’s reflectivity

43
Q

Is noise in a signal wanted or not wanted

A

Not wanted

44
Q

Is it essential to use deconvolution after migration?

A

Yes , slide 50 / 51 L5

45
Q

Sampling Data theory states that the sample rate, Fsamp, must be at least _____ of Fmax

A

Twice

Fsamp > 2Fmax

46
Q

in the sampling theory, what must you be able to sample?

A

The highest frequency in the data, Fmax

47
Q

May have to high the cut the sample data.

A

Ex) Slide 8 / 69 of L6

48
Q

if Fsamp = 500hz, what does dt =?

A

0.002sec

Fsamp = 1 / dt

49
Q

Aliasing : when ___

A

E(f) f > Fmax

50
Q

As t or f tend to ____; ____FT tends to a _____ FT

A

zero
discrete
continuous

51
Q

A periodic waveform is composed of what?

A

Sinusoids

52
Q

after correlation, of a vibrator sweep, is the line flat or or not?

A

it becomes flat

53
Q

is it okay to have no zeros in W(f)?

A

Yes it is Ok to have a smooth W(f) with no zeros Wsm(f)

slide 17 / 69 L6

GeoPhysics (9 decks)

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