Gravity Structural Inversion for Salt Body?

MartinVogele

Dear community,

I am a newbie in setting up 3D models for gravity inversion and forward modelling and need your advice on how to structurally inverted for the top of salt surface w/o using VALEM?

(1) The input surfaces I use for structural Inversion are very conceptual as I do not have seismic data to further constrain them. Can the inverted surface cut through above/below laying surfaces if this is required to minimise the misfit between modelled and observed gravity?

(2) Is there a workaround to structurally invert for a feature within my model that is modelled with a surface + 3D body, e.g. salt w/o using VALEM? If not, I was thinking of first running a structural inversion to constrain the level of the top salt in areas w/o multi-z values, e.g. diapir and then somehow run an iterative density inversion for the individual layers above the salt to model the reduced density minimum where the salt diapir is expected?

(3) Is there a way to create 2D cross-sections through a set-up 3D model to use as input for GM-SYS 2D Forward modelling?



Sorry for the inconvenience in case the answer to my question is trivial and thank you very much for your support!

Martin

GaudPouliquen

Hi @MartinVoegele ,

Here are a few answers to your questions:

(1) Yes - your inverted surface can go through others surface as long as 1- you set these layers as "pierceable" in your model, 2- the density within adjacent layers are defined either by constant density, lateral density distribution or a depth-density function, and not a voxel. The same apply to the density assigned to the layer you want to invert on since GM-SYS 3D doesn't support structural inversion for a layer which density distribution is defined by a voxel (hence VALEM).

(2) Instead of using a closed geosurface, i.e. body, you can represent your diapir with top and bottom layers ( which coincides outside the diapir area) and use a constraint grid in GM-SYS 3D to fix areas where you don't want your inverted surface to move.

(3) Yes you can do this easily: in your GM-SYS 3D model, go to the Display menu then Extract Profile Model from 3D Model, it'll prompt you to interactively select a profile on a map and the GM-SYS Profile model will be created.

I'm happy to discuss this further, and/or have a look at your model if you can share it.
Gaud

MartinVogele

Super - thanks a lot Gaud. Very much appreciated!
Cheers