3d effects in TDEM

Hi all,

I want to evaluate 3d effects in 1d inversion in TDEM. In other words, I want to calculate a forward response for a general 3d model and then invert the modeled data in 1d.

To start somehow, I’ve tried to modify the TDEM exapmles found at the SimPEG webpage, e.g. the “EM: TDEM: 1D: Inversion with VTEM waveform” However, I’ve got completely lost during the inversion part.

I’ve created the tensor mesh and assigned conductivities. Plotting the slice suggests everything is fine up to now (line 66). Also the forward response is somehow calculated. However, I’m not able toi set up the inversion for 1d, I always ends up with dimension mismatch, but I’m not able to figure out, where is the problem. Might be it is connected with the dmisfit (line 109)?

3dmesh.py.pdf (36.3 KB)

Could someone help me, please? I’m completely lost.

Thank you,

P.S. By the way, how to attach a text file? Just images are allowed by the upload function…

Hi @Jan, apologies for the late reply! Here is an example that might be more in line with what you are trying to achieve: https://github.com/simpeg-research/heagy-2018-aem. In this example, we ran a 3D forward simulation and inverted the TDEM data in 1D (and in 2D). There is a short paper that accompanies it (paper, arxiv). For 1D inversions, I would also encourage you to take a look at SimPEG EM1D (led by @sgkang09). We will eventually bring it into the main SimPEG repo, but for now it is a standalone package.

(and for the uploading - that was a setting I just changed… so I think you now should be able to upload .tex files and .py files. Sorry about that! Still learning a few things with discourse).

Hi Lindsey,

Many thanks for both answers! I’ve checked the SimPEG 1D and I like the built-in definition of common TDEM instrumetns. Do you have also the specifications of the WalkTEM instrument from the ABEM to be included?

Hi,Iheagy, about SimPEG EM1D , does the code can be used in the whole space situation, I want replace the air domain to seawater , so,I can use the seam code in the marine TEM, I know we can change the sigma value of inactive cell easily in 2D and 3D domamin, but in the 1D situation, I do not know how to change it.

Hi @zhongmin, apologies for the late reply! Are you planning to use grounded sources? If so, I would encourage you to take a look at empymod for 1D modelling which is led by @prisae

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