How to use xmeshfem2D with external model ?

[ICNSK]

Hi,
I am brand new user and trying to learn how to run xspecfem2D my research work. In the past I used finite difference simulators, which were limited to acoustic mode. I have input model for finite difference simulations, which is regularly samples binary file N1 x N2 and not sure how to convert it to mesh and model which could be used in xspecfem2D.

I was planning to use xmeshfem2D but could not find an example of how to use it with external mode.

Any information will be greatly appreciated, Thank you in advance

[homnath]

Hello, Is your finite difference model homogeneous or heterogeneous? Specfem2D cannot directly take the finite difference model input. However, you can construct similar model. A few years ago, I wrote a simple program which can convert finite difference models into specfem2d or specfem3d files. https://github.com/homnath/MeshAssist/blob/master/src/vti2cell.c But depending on your model, it may be easier to construct a model using xmeshfem2D. Please take a look at EXAMPLES/ folder. Best, Hom Nath

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--------------------------------------- Hom Nath Gharti, PhD Assistant Professor | Digital Earth Scientist https://www.digitalearthscience.com/ Department of Geological Sciences and Geological Engineering Miller Hall 314, 36 Union St Queen’s University Kingston, ON K7L 3N6, Canada Queen’s University is situated on traditional Anishinaabe and Haudenosaunee Territory.<https://www.queensu.ca/encyclopedia/t/traditional-territories>

________________________________ From: ICNSK ***@***.***> Sent: Friday, April 19, 2024 8:15 PM To: SPECFEM/specfem2d ***@***.***> Cc: Subscribed ***@***.***> Subject: [SPECFEM/specfem2d] How to use xmeshfem2D with external model ? (Discussion SPECFEM/specfem2d#1219) Hi, I am brand new user and trying to learn how to run xspecfem2D my research work. In the past I used finite difference simulators, which were limited to acoustic mode. I have input model for finite difference simulations, which is regularly samples binary file N1 x N2 and not sure how to convert it to mesh and model which could be used in xspecfem2D. I was planning to use xmeshfem2D but could not find an example of how to use it with external mode. Any information will be greatly appreciated, Thank you in advance — Reply to this email directly, view it on GitHub<https://github.com/SPECFEM/specfem2d/discussions/1219>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ABMCQ4XL5WXDBO7QJ5F4BQLY6GXQZAVCNFSM6AAAAABGP7ZWXCVHI2DSMVQWIX3LMV43ERDJONRXK43TNFXW4OZWGUZTAOBYGA>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[ICNSK]

Dear Hom Nath,

Thank you for reply ! My finite difference model is heterogeneous. In the EXAMPLES folder i found Marmousi mesh (from your previous work 2016/2023 ./EXAMPLES/Marmousi_mesh_of_the_model ) which could be a good starting point, but i was not able to locate PAR files with example how to use it. I have no experiences with mesh generation software, and i was hoping to bypass that step at first by using specfem2d functionality to create and read property files. Below are the conceptual steps i am considering for my first try. Please let me know if they makes any sense.

1. Create placeholder model using PAR file with dummy material properties and simple topography file. Model extent will correspond to extent of finite difference model ( key parameters are below).

MODEL = default
SAVE_MODEL = ascii
nbmodels = 1
1 1 2700.d0 3000.d0 1732.051d0 0 0 9999 9999 0 0 0 0 0 0
interfacesfile = simple_topo.topo (will have 1 layer with nz=30 elements)
nx=20
nbregions = 1
1	20 1 30 1

2. Than use xmeshfem2D which will create 20x30 mesh and use specfem2d to generate corresponding ./DATA/proc000000_rho_vp_vs.dat

3. Replace dummy values of rho, vp, vs by corresponding values from finite difference model based on XZ coordinates.

4. Run specfem2d with MODEL = ascii to perform simulation using updated ./DATA/proc000000_rho_vp_vs.dat

[homnath]

Can you try the example: EXAMPLES/simple_topography_and_also_a_simple_fluid_layer It uses an internal mesher. Best, Hom Nath

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--------------------------------------- Hom Nath Gharti, PhD Assistant Professor | Digital Earth Scientist https://www.digitalearthscience.com/ Department of Geological Sciences and Geological Engineering Miller Hall 314, 36 Union St Queen’s University Kingston, ON K7L 3N6, Canada Queen’s University is situated on traditional Anishinaabe and Haudenosaunee Territory.<https://www.queensu.ca/encyclopedia/t/traditional-territories>

________________________________ From: ICNSK ***@***.***> Sent: Saturday, April 20, 2024 12:15 PM To: SPECFEM/specfem2d ***@***.***> Cc: Hom Nath Gharti ***@***.***>; Comment ***@***.***> Subject: Re: [SPECFEM/specfem2d] How to use xmeshfem2D with external model ? (Discussion SPECFEM/specfem2d#1219) Dear Hom Nath, Thank you for reply ! My finite difference model is heterogeneous. In the EXAMPLES folder i found Marmousi mesh (from your previous work 2016/2023 ./EXAMPLES/Marmousi_mesh_of_the_model ) which could be a good starting point, but i was not able to locate PAR files with example how to use it. I have no experiences with mesh generation software, and i was hoping to bypass that step at first by using specfem2d functionality to create and read property files. Below are the conceptual steps i am considering for my first try. Please let me know if they makes any sense. 1. Create placeholder model using PAR file with dummy material properties and simple topography file. Model extent will correspond to extent of finite difference model ( key parameters are below). MODEL = default SAVE_MODEL = ascii nbmodels = 1 1 1 2700.d0 3000.d0 1732.051d0 0 0 9999 9999 0 0 0 0 0 0 interfacesfile = simple_topo.topo (will have 1 layer with nz=30 elements) nx=20 nbregions = 1 1 20 1 30 1 1. Than use xmeshfem2D which will create 20x30 mesh and use specfem2d to generate corresponding ./DATA/proc000000_rho_vp_vs.dat 2. Replace dummy values of rho, vp, vs by corresponding values from finite difference model based on XZ coordinates. 3. Run specfem2d with MODEL = ascii to perform simulation using updated ./DATA/proc000000_rho_vp_vs.dat — Reply to this email directly, view it on GitHub<https://github.com/SPECFEM/specfem2d/discussions/1219#discussioncomment-9175154>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ABMCQ4S3BSNVMDLKNVWFHV3Y6KIBDAVCNFSM6AAAAABGP7ZWXCVHI2DSMVQWIX3LMV43SRDJONRXK43TNFXW4Q3PNVWWK3TUHM4TCNZVGE2TI>. You are receiving this because you commented.Message ID: ***@***.***>

[ICNSK]

Dear @homnath,

Thank you for pointing me to a good example ! I was able to modify it and follow 2 step approach to update material properties and run simulation with Marmousi Elastic Model using rectangular grid produced by xmeshfem2D

[homnath]

Great! Congratulations!

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________________________________ From: ICNSK ***@***.***> Sent: Tuesday, April 23, 2024 6:36 PM To: SPECFEM/specfem2d ***@***.***> Cc: Hom Nath Gharti ***@***.***>; Mention ***@***.***> Subject: Re: [SPECFEM/specfem2d] How to use xmeshfem2D with external model ? (Discussion SPECFEM/specfem2d#1219) Dear @homnath<https://github.com/homnath>, Thank you for pointing me to a good example ! I was able to modify it and follow 2 step approach to update material properties and run simulation with Marmousi Elastic Model<https://www.geoazur.fr/WIND/bin/view/Main/Data/WebHome> using rectangular grid produced by xmeshfem2D image.png (view on web)<https://github.com/SPECFEM/specfem2d/assets/167325492/d73ff6e9-58e5-4a92-8fab-b852c4f41e9b> — Reply to this email directly, view it on GitHub<https://github.com/SPECFEM/specfem2d/discussions/1219#discussioncomment-9206071>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ABMCQ4WOEYVKO7ONGNXNUB3Y63O7DAVCNFSM6AAAAABGP7ZWXCVHI2DSMVQWIX3LMV43SRDJONRXK43TNFXW4Q3PNVWWK3TUHM4TEMBWGA3TC>. You are receiving this because you were mentioned.Message ID: ***@***.***>