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Benchmarks / Short-Term Crustal Dynamics / Benchmarks - OLD /

Benchmark 7 - OLD

Benchmark 7

Elastic solution for a circular strike-slip fault. The conceptual model is an elastic disk of radius 200 km, with a circular left-lateral strike-slip fault forming an inner plug which rotates inside the outer annulus. Because of the symmetry of the problem, radial displacements should vanish and only the first quadrant needs to be modeled. If required, a mesh using cylindrical coordinates can be downloaded from http://geoweb.mit.edu/fe/.

GOALS

  • Test techniques and implementation methods for non-planar faults (use of local vs. global coordinate systems, etc.)
  • Investigate the grid resolution required to properly resolve non-planar faults.
  • Test ability of various codes to model non-planar faults
  • Test implementation of boundary conditions in terms of Cartesian and Polar coordinates.
  • Code comparison

DETAILED DESCRIPTION

  • Model size: Thickness = 40 km; 10 km ≤ r < 200 km; 0 ≤ θ ≤ π/2
  • Elastic material properties: Poisson solid, G = 30 GPa
  • Density and Gravity: None
  • Boundary conditions: Bottom pinned x-displacement pinned at y = 0 (i.e., θ = 0) y-displacement pinned at x = 0 (i.e., θ = π/2)
  • Coarse mesh node spacing: dr = dz = 2 km; dθ = 2 degrees
  • Fault specifications: Type: Vertical strike-slip Location: r = 100 km; -16 km ≤ z ≤ 0 km Slip distribution: 1 m of uniform left lateral slip from -12 km ≤ z ≤ 0 km with a linear taper to 0 slip at fault tip (z = -16 km)

REQUESTED OUTPUT AND RESULTS

Mesh Variations: As memory, time, and patience allow, run models at 1/2, 1/4, and 1/8, etc. the original coarse mesh spacing, investigate variable mesh spacing, and/or employ a variety of element types.

For All Benchmark Variations:

  • Stresses and displacements along a line running radially at θ = 45 degrees, and lines running with constant r = 95, 99, 101, and 105 km, at depths of 0, 12, 16, 17 and 21 below the surface, all results at times of 0, 1, 5 and 10 years.
  • CPU time, wallclock time, memory usage info, compiler info, and platform info

TRUTH

The ‘best’ answer will be derived via mesh refinement. There will also be a solution generated using Okada point sources in an infinite halfspace.

ADDITIONAL NOTES

None


LaGrit Files

Benchmark problem definitions: http://www-gpsg.mit.edu/fe/Meshes.html

BENCHMARK 7 MESH GENERATION

A series of meshes of different resolution have been built to represent the BM7 model domain. The grids above are available in AVS and GMV format. See the image gallery for pictures of the mesh.

Build a 2D triangulation and smooth the triangles

  • LaGriT Command File: bm7_cyl_pts2.lgi
  • OUTPUT: id_fault.inp
  • id_fault.gmv

Note: The control file bm7_cyl_pts2.lgi

Smooth the triangles:

  • LaGriT Command File: smooth.lgi
  • Input : id_fault.gmv
  • Output: s_r_mass1a.gmv

Stack the triangle layers to produce a tet mesh

  • LaGriT Command File: stack.lgi
  • Input : s_r_mass1a.gmv
  • Output: cmo_settet.inp
  • cmo_settet.gmv

Refine along the fault interface

  • LaGriT Command File: refine_tets.lgi
  • Input : cmo_settet.inp
  • Output:
    refine_interface1.( gmv / inp )
    refine_interface2.(gmv / inp )
    refine_interface3.( gmv / inp )
    refine_interface4.( gmv / inp )
    refine_interface5.( gmv / inp )
    refine_interface6.( gmv / inp )

All files (*.lgi *gmv *inp) in a single archive: File Size: 31.442698 Mbytes bm7_files.tar.gz

File Name #nodes #elements
cmo_settet.inp 16968 87219
id_fault.inp 1364 2589
refine_interface1.inp 21081 100773
refine_interface2.inp 25732 126516
refine_interface3.inp 30025 145379
refine_interface4.inp 36229 174108
refine_interface5.inp 42533 208931
refine_interface6.inp 47823 230242

GMV General Mesh Viewer Home Page

AVS UCD (*.inp) File format description


Image Gallery

A series of meshes of different resolution have been built to represent the BM7 model domain. The grids below are available in AVS and GMV format.

2d_no_smooth 2d_no_smooth_topview 2d_smooth 2d_smooth_topview
refine0 refine0_cut refine1 refine1_cut
refine1_farview refine2 refine2_cut refine3
refine3_cut refine4 refine4_cut refine5
refine5_cut refine6 refine6_cut refine6_farview

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