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OKUBO: Gravity change due to shear and tensile faults

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13 Jun 2012 (Updated )

Okubo's 1992 model for gravity change due to finite rectangular source in elastic half-space.

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Description

The Okubo [1992] model calculates analytical solution for gravity changes due to shear and tensile faults in an elastic half-space (as Okada [1985] does for deformations). This model can be used to simulate gravity anomalies produced by local perturbation like tectonic faults (earthquakes) or volcanic dykes (magmatic intrusion). Given rectangular fault geometry (length, width, depth, strike, dip) and 3-component dislocation amplitude (rake, slip and open), it computes the total gravity change (potential, cavity filling and free-air) at the free-surface.

The proposed Matlab script is a literal transcription of the Okubo's equations, except for the fault geometry that it is transposed in a geographical referential (East, North, Up), where the fault is defined by a strike angle relative to the North, and dislocation parameters are given by: rake, slip and opening (instead of U1, U2, U3), following Aki & Richards [1980] definition. All coordinates and depth are relative to fault centroid.

The equations are also vectorized for (x,y) coordinates and all parameters except dip angle.

Type "doc okubo92" for help, syntax and example, and see script comments for details.

Required Products MATLAB
MATLAB release MATLAB 7.14 (R2012a)
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Comments and Ratings (3)
26 Jul 2013 François Beauducel

Dear Martin,
Thanks for your feedback. The modification you made makes the function compatible with older version of Matlab (before 2009b, probably yours ?), but it adds warnings of the code analyser message indicator for any newer versions...
Anyway, I prefer to extend the backward compatibility so I will include your update.
Thanks again.
François.

12 Jul 2013 Martin Fuchs

I modified the scrip, now it works also for mee:
remove all ~ add dummy parameter:

function u=Sg(xi,eta,q,dip,nu) % dip,~)
function u=Dg(xi,eta,q,dip,nu) % dip,~)
function u=Tg(xi,eta,q,dip,nu) % dip,~)
function u=Cg(xi,eta,q,dip,nu) % dip,~)
function I=I2(xi,eta,q,R,nu) % dip,~)

regards Martin

10 Jul 2013 Martin Fuchs

I have problems using the code it says:

?? Error: File: okubo92.m Line: 249 Column: 28
Unexpected MATLAB operator.

When I look at this line I see:
function u=Tg(xi,eta,q,dip,~)

maybe the ~ is problematical

Updates
26 Apr 2013

- correction of a sign error on filling cavity effect
- BETA input parameter now usable...

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