Model:SNAC

SNAC

Also known as
Model type	Single
Model part of larger framework
Note on status model
Date note status model

Incorporated models or components:

Spatial dimensions	3D
Spatial extent	Continental, Landscape-Scale, Regional-Scale
Model domain	Terrestrial, Geodynamic
One-line model description	An updated Lagrangian explicit finite difference code for modeling a finitely deforming elasto-visco-plastic solid in 3D.
Extended model description	SNAC can solve momentum and heat energy balance equations in 3D solid with complicated rheology. Lagrangian description of motion adopted in SNAC makes it easy to monitor surface deformation during a crustal or continental scale tectonic event as well as introduce surface processes into a model.

Keywords:

Name	Eunseo Choi
Type of contact	Model developer
Institute / Organization	Lamont-Doherty Earth Observatory
Postal address 1	P.O. Box 1000
Postal address 2	61 Rt. 9W
Town / City	Palisades
Postal code	10964
State	New York
Country	United States
Email address	echoi@ldeo.columbia.edu
Phone	845-365-8813
Fax	845-365-8156

Supported platforms	Linux, Mac OS
Other platform
Programming language	C
Other program language
Code optimized	Single Processor, Multiple Processors
Multiple processors implemented
Nr of distributed processors
Nr of shared processors
Start year development	2003
Does model development still take place?	Yes
If above answer is no, provide end year model development
Code development status	Active
When did you indicate the 'code development status'?	2020
Model availability	As code
Source code availability (Or provide future intension)	Through web repository
Source web address	http://www.geodynamics.org/cig/software/snac/
Source csdms web address
Program license type	GPL v2
Program license type other
Memory requirements	tipically < 1 GB
Typical run time	hours to days

Describe input parameters	In XML format, the following groups of parameters are specified: simulation control group: total model time, time step, damping, etc. plugins: elasticity, viscoelasticity, temperature solver, etc. domain description group: domain size, element numbers, etc. initial and boundary conditions group
Input format	ASCII
Other input format	XML
Describe output parameters	Nodal field data: velocity, temperature Element-centered (discontinuous) field data: strain rate, stress, plastic strain, etc.
Output format	Binary
Other output format
Pre-processing software needed?	No
Describe pre-processing software
Post-processing software needed?	Yes
Describe post-processing software	A simple C program that converts binary outputs into ascii data file in the VTK format.
Visualization software needed?	Yes
If above answer is yes
Other visualization software	ParaView or anything that can visualize VTK files.

Describe processes represented by the model	Momentum balance in solid continuum under gravity and kinematic boundary conditions.
Describe key physical parameters and equations	Newton's second law in the dynamic form is damped to acquire static or quasi-static solutions. Among importance parameters are those for a constitutive model (elastic moduli, linear and non-linear viscosity, and parameters for strain-weakening plasticity) and damping parameters.
Describe length scale and resolution constraints	No inherent length scale or resolution as long as the continuum hypothesis is satisfied. A practical constraint on length scale and resolution is computational cost.
Describe time scale and resolution constraints	Time scale is essentially set by the Courant condition: practially by P-wave velocity or maxwell time according to the constitutive model being considered. However, the mass scaling technique allows significantly increased time steps values from the usual dynamic one.
Describe any numerical limitations and issues	Extreme deformation of mesh is expected during large deformationin the updated Lagrangian formulation but prevented by regridding. The numerical diffusion due to regridding, however, can sometime make structures (e.g. shear localization) lose desired sharpness. Regridding itself fails from time to time.

Describe available calibration data sets
Upload calibration data sets if available:
Describe available test data sets
Upload test data sets if available:
Describe ideal data for testing

Do you have current or future plans for collaborating with other researchers?

Is there a manual available?	Yes
Upload manual if available:	Media:Snac.pdf
Model website if any	http://www.geodynamics.org/cig/software/snac/
Model forum / discussion board

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Featured publication(s)	Year	Model described	Type of Reference	Citations
Choi, Eun-seo; Lavier, Luc; Gurnis, Michael; 2008. Thermomechanics of mid-ocean ridge segmentation. Physics of the Earth and Planetary Interiors, 171, 374–386. 10.1016/j.pepi.2008.08.010 (View/edit entry)	2008	SNAC	Model overview	68
Choi, Eunseo; Buck, W. Roger; 2012. Constraints on the strength of faults from the geometry of rider blocks in continental and oceanic core complexes: RIDER BLOCKS AND FAULT STRENGTH. Journal of Geophysical Research: Solid Earth, 117, n/a–n/a. 10.1029/2011JB008741 (View/edit entry)	2012	SNAC	Model application	39
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