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SPECFEM / specfem3d

SPECFEM3D_Cartesian simulates acoustic (fluid), elastic (solid), coupled acoustic/elastic, poroelastic or seismic wave propagation in any type of conforming mesh of hexahedra (structured or not).
GNU General Public License v3.0
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A question about the relative perturbation of model paramters #1461

Closed UM2020-create closed 3 years ago

UM2020-create commented 3 years ago

Hi,

I want to ask a question about the operator, ln( ), in the Eq. (8.15) of the user manual. It is writen as "where ln( ) is the natural logarithm". But in the paper of Tromp et al., 2005, take the Eq. 13 as an example. 'δ ln rho' means δrho/rho. I don't know which one is correct. Does this operator, ln( ), means logarithm or not?

Hope to get your answer, thanks a lot.

Geotomo commented 3 years ago

Hi, ln() indeed is logarithm, also "delta {ln rho} = {delta rho} / rho".

That is because (ln x)'=1/x.

At 2021-08-26 11:57:56, "UMCERI2020" @.***> wrote:

Hi,

I want to ask a question about the operator, ln( ), in the Eq. (8.15) of the user manual. It is writen as "where ln( ) is the natural logarithm". But in the paper of Tromp et al., 2005, take the Eq. 13 as an example. 'δ ln rho' means δrho/rho. I don't know which one is correct. Does this operator, ln( ), means logarithm or not?

Hope to get your answer, thanks a lot.

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UM2020-create commented 3 years ago

Thank you very much for your explanation!