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Rachel

Stereostat Paleostress Analysis

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Hi,

I have fault population data and I am trying to generate the stress axes Sig1, Sig2, and Sig3. In the help, it says that this is an option when checking "special data" but I don't see it anywhere. "Principal component axes" is not the same thing, I don't think.

Any help would be appreciated.

Thanks,

Rachel

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Hi Rachel,

The axes σ1 σ2 and σ3 are the principle component axes according to my structural geology book.

If a body is stationary under a system of forces, it is possible to choose at any point three mutually perpendicular planes, intersecting in the point and so orientated that the resultant stresses on the planes are wholly normal stresses or tractions. The three lines along which the planes intersect are known as the principal axes of stress and the stresses acting along them are the principal stresses at the point considered. in the general case the principal stresses are unequal, so we have maximum principal stress (σ1), the mean principal stress (σ2), and the minimum principal stress (σ3) at the point considered.

Hills, E. Sherbon, Elements of Structural Geology, John Wiley & Sons, Inc., Second Edition, 1972, p. 83.

Here are the results from StereoStat.

Results of Principal Component analysis:

Number of analyzed data: 38

PCA vector number: 1

--Orientation (az, pl): (324, 4)

--Eigenvalue: 0.650338

PCA vector number: 2

--Orientation (az, pl): (204, 81)

--Eigenvalue: 0.224361

PCA vector number: 3

--Orientation (az, pl): (54, 8)

--Eigenvalue: 0.125301

Thanks,

Tom B

RockWare Inc

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