<p>Estimating the velocity (or any other parameter) of the medium from seismic traces is an inverse problem. Different ways of formulating it exist,based on the experimental setting.</p>
<p>Let's start with something simple. In near surface studies, refraction is commonly used. A series of sensors (geophones) are laid out in a straight line, a seismic wave can be excited by using a hammer strike (the most common in near surface), a weight drop or a vibrating mass. Critical refraction occurs when the seismic wave encounters a higher velocity layer, the wave propagates along the interface between the the two layers, and is recorded at the surface. If one picks the first break (the time at which the waves arrives) for each trace, a slope can be calculated, this slope is the inverse of the apparent velocity (not the true velocity). Using these slopes, methods exist to estimated the depth to the refractor as well as the velocities. Google &quot;Refraction seismic&quot; for more details.</p>
<p>Tomography can be carried out as well, where the first break times are used to infer the velocity of the medium. Goolge &quot;Travel time tomography&quot; for more details.</p>
<p>Another way: The entire waveforms may be used, this is most commonly used at exploration scale seismic experiments. This inverse problem is a bit more complicated, and is very ill posed, however the result (if done right) are astoundingly high resolution. Google &quot;Full waveform inversion&quot; for more details.</p>
<p>This is a very brief, and incomplete overview. If you wish more details about any of the methods mentioned, I will be happy to provide them here. In case the application you had in mind does not fall in the categories I mentioned, share it with us, and I (or someone else) will answer you.</p>

CC BY-SA 4.0
2024-06-21T07:16:57.280Z
2024-06-21T07:16:57.280Z
Mustapha Benziane
<p>How can seismologists estimate velocity (on the different layers) of the wave propogated through the earth , only from given seismic trace(s) ?</p>

CC BY-SA 4.0
2022-10-19T15:44:11.853Z
Well, technically you can't do anything with what you've listed here (other than analyze the spectral characteristics of the trace). At the very least, data such as offset, estimated location of epicenter+focus, and time are required. Perhaps that's what you're getting at, but I'd suggest refining the details of the question more!
nate
<seismology><seismic>
Estimation of velocity of the wave from seismic trace
Fearless_Wolf
# Estimation of velocity of the wave from seismic trace

(Asked by: username_0 on 2022-09-15)

How can seismologists estimate velocity (on the different layers) of the wave propogated through the earth , only from given seismic trace(s) ?

**Tags:** seismology, seismic

> **Comments:**
> **username_1**: Well, technically you can't do anything with what you've listed here (other than analyze the spectral characteristics of the trace). At the very least, data such as offset, estimated location of epicenter+focus, and time are required. Perhaps that's what you're getting at, but I'd suggest refining the details of the question more!  

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## 1 answers

### Answer by username_2 on 2024-06-21. Score: 1

Estimating the velocity (or any other parameter) of the medium from seismic traces is an inverse problem. Different ways of formulating it exist,based on the experimental setting.

Let's start with something simple. In near surface studies, refraction is commonly used. A series of sensors (geophones) are laid out in a straight line, a seismic wave can be excited by using a hammer strike (the most common in near surface), a weight drop or a vibrating mass. Critical refraction occurs when the seismic wave encounters a higher velocity layer, the wave propagates along the interface between the the two layers, and is recorded at the surface. If one picks the first break (the time at which the waves arrives) for each trace, a slope can be calculated, this slope is the inverse of the apparent velocity (not the true velocity). Using these slopes, methods exist to estimated the depth to the refractor as well as the velocities. Google "Refraction seismic" for more details.

Tomography can be carried out as well, where the first break times are used to infer the velocity of the medium. Goolge "Travel time tomography" for more details.

Another way: The entire waveforms may be used, this is most commonly used at exploration scale seismic experiments. This inverse problem is a bit more complicated, and is very ill posed, however the result (if done right) are astoundingly high resolution. Google "Full waveform inversion" for more details.

This is a very brief, and incomplete overview. If you wish more details about any of the methods mentioned, I will be happy to provide them here. In case the application you had in mind does not fall in the categories I mentioned, share it with us, and I (or someone else) will answer you.


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