## calculate compressibility with depth and seismic velocity

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Geronimo234
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Joined: Tue Jan 12, 2016 11:22 am

### calculate compressibility with depth and seismic velocity

Hi there,

I need to calculate or estimate the compressibility from an area in the Northern German Basin. Somebody gave me the hint to look in the work from Jaritz et al. 1991, where he is descriping the seismic velocities depending on the deepth.
So I have the seismic velocities for each layer in the Basin and the depth from the start and the beginning of the layer, but I'm wondering how to get information about the compressibility ( K=(∆V/∆p)/V ) with that parameters.

Jaritz is only working with the p-waves, so I was told to find plausible values for the Poisson's ratio or the Vs/Vp relationship.

Is there anybody who can help me with this problem?

Greets and thank you,

Geronimo234

geophix
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Joined: Fri Jul 24, 2009 9:26 am

### Re: calculate compressibility with depth and seismic velocity

You need to use the formulas in the second page of the following pdf file. Basically you need to know P and S wave velocities and density to calculate shear modulus and bulk modulus.

https://pangea.stanford.edu/courses/gp2 ... ncepts.pdf

Geronimo234
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Posts: 3
Joined: Tue Jan 12, 2016 11:22 am

### Re: calculate compressibility with depth and seismic velocity

Hi,

thank you very much for the formular!
The problem is that I only have Vp, so the P waves velocities..there is no way to find Vs, I'll try to find them, but in case there are no values, is there a posibility to calculate K without Vs or at least to estimate correct values?

geophix
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Joined: Fri Jul 24, 2009 9:26 am

### Re: calculate compressibility with depth and seismic velocity

I guess you have to estimate Vs from Vp using experienced data. You can google relationships of Vp and Vs in some situations such as saturated sandstone, etc, whichever fitting the geology of your model.

Geronimo234
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Posts: 3
Joined: Tue Jan 12, 2016 11:22 am

### Re: calculate compressibility with depth and seismic velocity

I found some data, hopefully they'll do it. Got the compressibility now and I will check them tomorrow.

Thank you very much for your help!

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