# [CIG-SHORT] comment on resolution of benchmark problems

Carl W. Gable gable at lanl.gov
Tue Jul 18 13:04:20 PDT 2006

```I'd like some feedback on what type of mesh
size is going to be realistic for the benchmark
calculations. The definition talks about using
125m resolution if possible. Uniform elements
will require about 42,000,000 elements for that
resolution.

A back of the envelope calculation shows that
for the strike slip and reverse fault problem
you have a fault that is a plane apx. 16km x 16km.
If you line just the face of the fault with 125m
spaced nodes, and then also put a plane of nodes
of the same resolution above and below the fault
you have:

16*8*16*8 = 16,384 nodes for a single plane.

For three planes of nodes you have:
49152 nodes.

If you connect those up to form tetrahedra
you will get about 2*6*49152 = 589,826 tets
just to mesh the fault plane.

So even with an adaptive strategy to only
refine the fault the number of elements is
going to hit 1,000,000 very quickly. Is
this going to be realistic for computations?

Even the regular mesh calculations will have:
(the factor for number of elements is between 5-6)

1000m resolution =>    24*24*24*6 =    82944 elements
500m resolution =>    48*48*48*6 =   663552 elements
250m resolution =>    96*96*96*6 =  5308416 elements
125m resolution => 192*192*192*6 = 42467328 elements

Carl

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Dr. Carl W. Gable, Staff Scientist

Voice 505-665-3533 Fax   505-665-8737
Email gable at lanl.gov
http://www.ees.lanl.gov/staff/gable

EES-6, MS T003
Los Alamos National Laboratory
Los Alamos NM 87545

Hydrology, Geochemistry & Geology Group (EES-6)
Focus: Geophysics, Hydrology, Mesh Generation
Correspondence / TSPA
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