BBP CyberShake 2015
Computational Details
We have a copy of BBP installed on Blue Waters; the two codes are in /u/sciteam/scottcal/scratch/bbp/15.3.0/bbp/src/gp/WccFormat/Progs . Alternatively, if you have a recent version of the BBP installed, you should be able to find it in your install under <version#>/bbp/src/gp/WccFormat/Progs .It sounds like it would probably be best to use the current version of the code, though, and then just run the site response for all events.
We checked with David Gill, and the version of CVM-S4.26 we used for CyberShake Study 15.4 does include the GTL, with a 500 m/s minimum cutoff. It sounds like it would be better to extract Vs30 values from it rather than Wills. Should we apply the 500 m/s cutoff to the Vs30 values we pass to site response like we did with CyberShake, or use them as-is?
Site response module: wcc_siteamp. I'm not sure what is the difference btw the 2 versions on the BBP. Can you point me to where the source codes are (or send them to me) and I'll take a look?
In any case, the current version of the code uses site amplification factors based on the 2014 NGA GMPEs and I'm sure that is not on the BBP. However, aside from some simple tests, I have not formally validated this version (e.g. by redoing the GP2010 validations, although that is on my to-do list...). I'm OK with using it though, but we'd need to make sure to run some compatibility checks just to make sure the results looked OK.
...but it sounds like we should only do it if the Vs30 for the site is below 600-700 m/s.
Actually, I would recommend just applying the modification to all sites without worrying about the specific Vs30. For sites that have Vs30 greater than about 600-700 the modification will be very minor. But the extra overhead in running the code for all sites is probably insignificant relative to the (equally trivial) overhead in checking the sites for an arbitrary Vs30 threshold and having different processing streams based on this.
A related question - in 2011 we pulled the Vs30 values from Wills. Is that still correct, or should we use Vs30 from the velocity model we used for the CyberShake deterministic (CVM-S4.26)?
There are some concerns about the near-surface velocity values in the CVM used for the previous calcualtions, in particular, very high Vs for rock sites, and that is why we used Wills I'm not sure what is in CVM-S4.26, does it include the "geotechnical layer"? If so, then its probably best to use these values, so that the LF and HF portions are consistent.
Program Name: wcc_siteamp14.c
The input and output are the same as previous versions with the possible exception being the parameter "model". If "model" is not specified, then the default settings are used, which is fine.
Check to see if this parameter was set previously. (i.e., as model=<something> either in a parfile or on the command line)
Regarding the question of whether we should we apply the 500 m/s cutoff to the Vs30 values we pass to site response like we did with CyberShake, or use them as-is? Current decision is to use them as is. There will be an apparent disconnect with the 500 m/s cutoff at some sites, although the the 500 m/s value with a 100 meter grid spacing is an adequate approximation for the LF calculation.
Priority CyberShake Sites of Interest
Broadband-Cybershake motions for a few sites combining the stochastic and Cybershake signals:
- STNI - basin site
- LADT - basin site
- PAS - rock site
- WNGC - between basins, with expected high ground motions
- LADP - another rock site, near fault
