Skip to main content
14 votes
Accepted

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 ...
bon's user avatar
  • 2,211
8 votes
Accepted

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 ...
Matt Hall's user avatar
  • 11k
7 votes
Accepted

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 ...
Way of the Geophysicist's user avatar
6 votes
Accepted

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 ...
Matt Hall's user avatar
  • 11k
6 votes
Accepted

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-...
Matt Hall's user avatar
  • 11k
5 votes
Accepted

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 ...
Antonio's user avatar
  • 947
4 votes
Accepted

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....
Erik's user avatar
  • 1,999
4 votes
Accepted

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. ...
bon's user avatar
  • 2,211
4 votes
Accepted

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-...
Way of the Geophysicist's user avatar
4 votes
Accepted

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 (...
Erik's user avatar
  • 1,999
4 votes

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 ...
uhoh's user avatar
  • 7,122
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 ...
Erik's user avatar
  • 1,999
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, ...
Fred's user avatar
  • 24.7k
3 votes
Accepted

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 ...
Antonio's user avatar
  • 947
3 votes
Accepted

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 ...
stevej's user avatar
  • 1,044
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 ...
Coastal's user avatar
  • 146
3 votes
Accepted

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 ...
user2821's user avatar
  • 5,946
3 votes
Accepted

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)...
Gordon Stanger's user avatar
3 votes
Accepted

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 ...
Erik's user avatar
  • 1,999
3 votes
Accepted

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 ...
V-Red's user avatar
  • 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 ...
Rory Alsop's user avatar
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') ...
nate's user avatar
  • 796
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 ...
dvoytan's user avatar
  • 121
3 votes

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....
Erik's user avatar
  • 1,999
3 votes
Accepted

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 ...
Spencer's user avatar
  • 3,638
3 votes
Accepted

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 ...
Stevan V. Saban's user avatar
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 (...
E L's user avatar
  • 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, ...
Gabriel Perez's user avatar
2 votes

What percentage of the earth's surface is covered by 2D or 3D reflection seismic data?

I don't know the exact percentage. But it is way more than just oil fields, EarthScope has done most of the continental US. http://www.usarray.org/researchers/obs/transportable
Neo's user avatar
  • 6,456
2 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 ...
Vikki's user avatar
  • 317

Only top scored, non community-wiki answers of a minimum length are eligible