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

Charles Williams willic3 at rpi.edu
Tue Jul 18 13:29:23 PDT 2006

```I'm guessing Carl's meshes are identical to mine.  I'm attaching my
lagrit script for the strike-slip benchmark for reference.  I put in
a few surfaces corresponding to the fault edges, etc., but due to the
very regular nature of these problems, I don't think they made any
difference in the mesh.

Charles

￼
On Jul 18, 2006, at 4:20 PM, Brad Aagaard wrote:

> Carl-
>
> Charles already constructed uniform meshes for both the reverse and
> strike-slip cases at resolutions of 1000m, 500m, and 250m. Charles
> plans to look at your strike-slip meshes and compare them to his. At
> this point, PyLith is hogging memory and the 500m resolution is about
> the max doable. Hopefully this will change in the next week and the
> 250m resolution will be possible.
>
> For variable resolution, the goal is to achieve a more accurate
> solution using a variable resolution with the same number of nodes as
> the uniform resolutions.
>
>
>
> On Tuesday 18 July 2006 1:04 pm, Carl W. Gable wrote:
>> 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
>>
>>
>> ----------------------------------
>> 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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>

Charles A. Williams
Dept. of Earth & Environmental Sciences
Science Center, 2C01B
Rensselaer Polytechnic Institute
Troy, NY  12180
Phone:    (518) 276-3369
FAX:        (518) 276-2012
e-mail:    willic3 at rpi.edu

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