[CIG-SHORT] update on benchmarks

[Brad Aagaard]

Hi all:

Charles Williams and I have been spending some time scrutinizing the 
results from the strike-slip benchmark. We think we have finally zeroed 
in on a couple of problems. The most significant issue is that the 
benchmark description does not specify what to do where the two taper 
regions overlap. The supplied Matlab scripts for computing the 
analytical solution uses the minimum of the two tapers (maintaining a 
linear taper with respect to either y or z). Charles has been using a 
quadratic taper (product of the two linear tapers) which is why the 
GeoFEST results computed in late Nov have not been agreeing with the 
PyLith results. In the next few days, we should have new PyLith results 
with much better agreement for the strike-slip results.

Unfortunately, this taper issue also affects the reverse-slip benchmark 
results for BOTH GeoFEST and PyLith (and perhaps COMSOL/Femlab as 
well?). Greg Lyzenga used the PyLith input files in setting up the 
GeoFEST runs for this benchmark, and since Charles used a quadratic 
taper, the taper in the simulations doesn't match the taper in the 
analytical solution. So we should be able to reduce the misfit with 
respect to the analytical solution by redoing the benchmarks with the 
correct taper.

Charles is working on fixing the PyLith input files for the two 
benchmarks. Once we run the strike-slip benchmark and verify everything 
is as we expect, we will need someone to fix the GeoFEST reverse-slip 
input files and rerun the reverse-slip benchmark for each of the three 
resolutions. Any volunteers?

We all need to thanks Charles for staring at a bunch of numbers for more 
hours than he would have liked in order to get to the bottom of this!

Brad