Jayne Bormann (Bill Hammond’s student) sent two velocity fields on a uniform grid constructed from their test exercise using CMM4. Here they are. One is for a block model with geologic slip constraints and the other is without geologic constraints.

March 1, 2011

Bill Hammond and Jayne Bormann sent a new model covering a wider area

Hi David --

I hope the attached velocity file on a grid works for your comparison.  Its constructed by taking the block model geometries and velocity field provided by Kaj Johnson for the UCERF exercise.  We have not adjusted any block boundaries or done any viscoelastic corrections, etc. We used my block modeling code to get a solution and then predict velocities on a regular 0.1˚ x 0.1˚ grid from -121.9 to -114.1 longitude, 32 to 37.2 latitude.

File is longitude, latitude, veast, vnorth.
(degrees, degrees, mm/yr, mm/yr)

Let us know if you have any questions about the file or model.  Thanks for including us.

Cheers,
-Bill 

David --

I think there are several possible answers to your question.  Some thoughts:

Short answer: some could be real, some are bogus.

Some strain concentrations are little blips and speckles that are probably numerical errors which occurred as single isolated pixels of the velocity field. I noticed a few of these in the velocity field i was about to send you and did a quick 'despeckle' by smoothing those out. I think it happens when an evaluation point occurs right on a block boundary/fault segment end, but I'm not sure yet....looking into it.   It shouldn't occur since we assume all faults are locked at the surface, so is an error, but it shouldn't effect the rest of the strain patterns in the model.

Second, some folks explicitly handle surface creep (we do not).  That is they allow the locking depth to go to zero where they think that is justified.  Like the harvard model in the central san andreas, strain is very low on the flanks but extremely high right at the fault.  There are places where maybe their solution is going for shallow locking depths if not all the way to zero.  We did not adjust the locking depths in our solution so all are 15 km.

In some cases its a real difficulty with block modeling because at a three fault segment intersection (e.g. at east Garlock and southern Panamint fault intersection point in the harvard model) the rectangular fault planes cannot all fit together well at depth...theoretically they could giving more attention, but most folks probably don't deal with the intersections perfectly.  

I'll send a description soon.

-Bill