14
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What are the distinguishing features of an "artificial seismic wave" (e.g. a large underground explosion)
Several things can indicate that a seismic event is an explosion and not an earthquake.
Firstly, the depth of the source. The shallowest earthquakes tend to have a hypocentre that is at least a ...
- 2,221
8
votes
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SEGD and SEGY recorded data
SEG-D is a specialized format, while SEG-Y is a general-purpose format.
In general, SEG-D is intended for field recordings of seismic data, and SEG-Y is intended for 'seismic data exchange'. Having ...
- 11k
7
votes
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What is the relationship between raw seismic data, CMP Stacking, NMO & Machine Learning
SEG-Y files are a general purpose archival format. So they can be "anything". 2D seismic, 3D seismic, raw, processed, unstacked or even derivatives (seismic attributes).
How to get information about ...
6
votes
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Predicting rock type from seismic processing
This is a ginormous question; a complete answer is probably worth an MSc in exploration geophysics. But I can try to give some pointers for places to find out more.
Preface: in general, considering ...
- 11k
6
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What is the purpose of wavelet extraction from the seismic trace?
We're usually not interested in the wavelet per se, but we need to know it in order to understand how the seismic trace relates to geological properties we are interested in.
According to the so-...
- 11k
5
votes
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Seismic data spectral analysis
Typically seismic data should oscillate around 0 amplitude in the time domain, i.e. there should be just as much positive amplitude as there is negative (otherwise the ground would have had a net ...
- 947
5
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Using the Born approximation in seismic inversion
The best reference on this is:
J.A. Hudson and J.R. Heritage, 1981, The use of the Born approximation in seismic scattering problems, Geophys. J. R. Astr. Soc., v.66, 221-240.
Basically, the Born ...
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4
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Why is a mild earthquake often mistaken as dizziness or vertigo?
Having experienced many minor earthquakes (Mag 3 to 5 in the East African Rift Valley, Samoa, Solomon Islands, Philippines and Indonesia), and one major life-threatening earthquake (Magnitude 8, Nepal)...
- 14.2k
4
votes
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Which type of seismic sensors usually used in Earthquake Early Warning?
Accelerometers, preferably triaxial (i.e., those that record horizontal and vertical motion). Beyond that your question is indeed a bit too open-ended. Some use many cheap MEMS (http://onlinelibrary....
- 1,989
4
votes
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Seismic migration concepts
The information you provide is rather limited, however, I want to try and disentangle this. The way I see it, you are mixing three different concepts in your questions. I will work through the semi-...
4
votes
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Seismic inversion: High-Frequency approximation
The propagation of seismic waves is described by the wave equation: $$\mathrm{\nabla \cdot \sigma = \frac{\partial ^2 u}{\partial t^2}}$$
Where $\sigma$ is the stress and $u$ is the displacement.
...
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4
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How to read Seismic Survey?
Oh boy, a thorough understanding will be difficult, because reading these things to their full potential can take 10+ years of experience... If you really want to dive into it, read a book on seismic (...
- 1,989
4
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wavelength of seismic wave with a gaussian source
The Fourier transform of a Gaussian is a Gaussian.
If your signal is given by
$$g(t)=\frac{1}{\sqrt{2 \pi \sigma^2}} \exp\left( -\frac{(t-t_0)^2}{2 \sigma^2}\right)$$
then your frequency spectrum ...
- 7,074
4
votes
stretch phenomena after NMO application on seismic data
My understanding is the following (NB: it could be wrong!).
The assumption is that on a common shot gather, your travel time follows a hyperbolic curve:
$$
f(x)=t^2=t_0^2 + \frac{x^2}{v^2},
$$
where ...
- 1,989
3
votes
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Seismic Reflectivity and Fractal (Random) Behavior
The assumption that the earth's reflectivity is random (i.e. has a white spectrum) is only necessary for the statistical extraction of a wavelet from the data itself via the amplitude spectrum of the ...
- 947
3
votes
What are the distinguishing features of an "artificial seismic wave" (e.g. a large underground explosion)
A bit more information - total plagiarism from
Q&A: what earthquake science can tell us about North Korea’s nuclear test.
Any sort of earthquake or explosion, whether natural or man-made, ...
- 24.6k
3
votes
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What is trace-based seismic Inversion
I too have found this nomenclature rather confusing. I am pretty sure that trace-based inversion is merely where each seismic trace is inverted independently of surrounding traces. This would take ...
- 1,044
3
votes
Why is a mild earthquake often mistaken as dizziness or vertigo?
When a bus or truck goes by, you typically hear it before you feel it, so you already know what it is before any noticeable ground motion starts, and your brain accepts the shaking as being due to the ...
- 327
3
votes
What percentage of the earth's surface is covered by 2D or 3D reflection seismic data?
Perhaps an easier question would be - what percentage of the earth has discovered oil/gas fields! This data should be easier to find than the surveys themselves, and can probably give you a rough ...
- 146
3
votes
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Detecting seismic waves using Software Defined Radio
I hope I understand your question right, I think there are some confusion about frequency range and wave-types.
Seismic waves are acceleration of matter that transfer kinetic energy from a seismic ...
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3
votes
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Basic petrophysics
The concept of pore pressure is identical to the concept of pore fluid pressure, as you identified yourself.
The article rightfully identifies two pressure types: the confining pressure (those forces ...
- 1,989
3
votes
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Quality control in Seismic Acquisition - How much data is required?
After a more elaborate literature survey, it turns out that there are two types of quality control that can be performed on seismic data. One is of the acquisition parameters [1], which are just a few ...
- 141
3
votes
Travel Times for Seismic Wave Types - Why reflected t-x plot curves
This is conceptually relatively simple if you look at where the reflection (and refraction) happen, and in fact you have articulated the key concept in your question:
The reflected wave ...Over ...
- 278
3
votes
What is the vertical axis of this waveform shown in this tweeted IRIS GIF?
Answer 1
The horizontal axis is indeed time (don't forget units and note how long those periods are!). As for the vertical axis, I'm certain that this is displaying vertical (or 'Z' or 'V') ...
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3
votes
Why do P waves have a higher velocity in the lower mantle than in the core even though the core has a much higher density?
tldr; Increased density corresponds with decreased P-wave velocity
The P-wave velocity for an isotropic medium is:
$$
V_p = \sqrt\frac{K+4/3\mu}{\rho}
$$
where $K$ is the Bulk Modulus, $\mu$ is the ...
- 121
3
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How do we know the speed of S-waves (shear waves) in the Earth's inner core? Has this been measured?
If waves would travel only through a medium while keeping their form (i.e., P-waves remain P-waves and S-waves remain S-waves), you would obtain something a bit like this video: https://www.youtube....
- 1,989
3
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Is there a seismic discontinuity between the lithosphere and asthenosphere?
Short answer: There are actually two different Gutenberg discontinuities, and one of them corresponds to one way of defining the Lithosphere-asthenosphere boundary, or LAB.
(The abstract of this ...
- 3,548
3
votes
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How to produce random numbers from seismic data?
This quote is from the article:
Use of Local Entropy: after collecting data from the external sources, it is necessary to generate entropy locally. For that, we use our own TRNG (True Random Number ...
- 263
2
votes
Cross-line fold of a towed-streamer survey
Crossline coverage is 1/2 the spread width. A survey is usually designed to deliver perfectly abutted crossline coverage (overlapping the spreads as the previous correspondent said). Common midpoint (...
- 21
2
votes
Cross-line fold of a towed-streamer survey
By midpoint range he refers to the size (length in the crossline direction) of the area in the subsurface that is illuminated by one pass of the boat. In a simple case of flat and parallel layers, ...
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