I need help in a seismic refraction experiment

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abdelgowad
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I need help in a seismic refraction experiment

Post by abdelgowad »

Dear all,
Recently, I did a seismic refraction experiment to study the subsurface soil below a collapsed building. In this study, I put the receivers on one side of the building and shots on the other side. I need help in what software I should use to interpret the acquired data and I will be thankful if someone shares some papers concerning such experiment.
thanks in advance.
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99thpercentile
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Re: I need help in a seismic refraction experiment

Post by 99thpercentile »

It is unclear from your post whether you have sufficient shot locations to even perform a seismic refraction tomography (SRT) survey. What software do you normally use for your SRT surveys? I currently use Rayfract.

https://www.rayfract.com/

Be aware that SRT software will attempt to give you an answer no matter how poor your survey design was. You need to ensure a thorough understanding of the method and survey design so that your interpretation of the results from the software aligns with the physics of the problem. From your description, I would guess that you do not have enough shot locations, and that the shot geometry was poor.
Ryan E. North, PhD, RPG, GISP
Principal Geophysicist
ISC Geoscience
ryan.e.north@iscgeoscience.com
abdelgowad
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Re: I need help in a seismic refraction experiment

Post by abdelgowad »

Thank you very much.
I am using the Rayfract but in the Demo version. The option to put the right geometry is inactive.
By the way, in your opinion, what is the minimum number of shots that could be enough to perform a rough SRT??
Thanks
Pete
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Re: I need help in a seismic refraction experiment

Post by Pete »

Hi,
How many times you have to stack depends on your source, distance, max depth, receivers, noise etc. you just need to try.
I would suggest to run at least one parallel line just past the house and if possible a cross line. That is a full line where you place the receivers from zero offset densely towards the house to also record reflections. Then move the receivers further away on the line and repeat depending on numbers of geophones and sampling rate.
hAJET2345
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Re: I need help in a seismic refraction experiment

Post by hAJET2345 »

How did the experiment go? best fence
99thpercentile
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Re: I need help in a seismic refraction experiment

Post by 99thpercentile »

For SRT, the depth of investigation is approximately 1/5 of the spread length while spatial resolution is approximately 1/2 to 1x the geophone spacing. For short locations, you would typically do three off end shots for each end of the spread and shot locations every 2 to 3 geophone locations along the spread.
Ryan E. North, PhD, RPG, GISP
Principal Geophysicist
ISC Geoscience
ryan.e.north@iscgeoscience.com
resour
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Re: I need help in a seismic refraction experiment

Post by resour »

Our free trial version has clearly described limitations. See our manual

https://rayfract.com/help/rayfract.pdf

on page 72 / chapter System limitations :

- will expire after 30 days or after 50 runs, whichever happens first
- supports up to 30 shots per profile only. You will need to renumber your shots as shot
number 0 to shot number 29.
- does not support topography specification
- does not allow selecting Line type Borehole spread/line in Header menu, Profile dialog
- does not support Crosshole/Downhole/Uphole/Walkaway VSP survey Smooth inversion, with WET tomography
- does not support interactive Wavepath Eikonal Traveltime WET tomography
processing
- does not support interactive pseudo-2D DeltatV and XTV inversion
- does not offer time-to-depth inversion methods Wavefront and CMP intercept-time
refraction
- does not offer Midpoint breaks display
- Trace|Midpoint gather is disabled
- does not support importing or specifying receiver station coordinates. Assumes
a straight line recorded on a flat topography.
- you need to specify shot and receiver position for horizontal refraction spread/line by station number during import of shots.
- you can select pre-defined receiver spread types or define your own receiver spread type in File menu, item New Spread type.
- does not support importing or specifying lateral shot position offsets and shot hole depths.

For our latest release notes see

https://rayfract.com/help/release_notes.pdf
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