CyberShake Study 22.12

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CyberShake Study 22.10 is a proposed study in Southern California which will include deterministic low-frequency (0-1 Hz) and stochastic high-frequency (1-50 Hz) simulations. We will use the Graves & Pitarka (2019) rupture generator and the high frequency modules from the SCEC Broadband Platform v22.4.

Status

This study is in the planning phase. We estimate calculations will begin in October 2022.

Data Products

Science Goals

Technical Goals

Sites

Velocity Model

We are planning to use CVM-S4.26 with a GTL applied, and the CVM-S4 1D background model outside of the region boundaries.

We are investigating applying the Ely-Jordan GTL down to 700 m instead of the default of 350m. We extracted profiles for a series of southern California CyberShake sites, with no GTL, a GTL applied down to 350m, and a GTL applied down to 700m.

Sites (the CVM-S4.26 basins are outlined in red):

GTL profile sites.png

These are for sites outside of the CVM-S4.26 basins:

Site No GTL 700m GTL Smaller value, extracted from mesh
LAPD
Cvmsi default LAPD.png
Cvmsi elygtl ely z 700m LAPD.png
LAPD ifless profile.png
s650
Cvmsi default s650.png
Cvmsi elygtl ely z 700m s650.png
s764
Cvmsi default s764.png
Cvmsi elygtl ely z 700m s764.png
S764 ifless profile.png
s568
Cvmsi default s568.png
Cvmsi elygtl ely z 700m s568.png
S568 ifless profile.png
s035
Cvmsi default s035.png
Cvmsi elygtl ely z 700m s035.png
S035 ifless profile.png
RIDG
Cvmsi default RIDG.png
Cvmsi elygtl ely z 700m RIDG.png
PERR
Cvmsi default PERR.png
Cvmsi elygtl ely z 700m PERR.png
PERR ifless profile.png
MRVY
Cvmsi default MRVY.png
Cvmsi elygtl ely z 700m MRVY.png
MRVY ifless profile.png
s211
Cvmsi default s211.png
Cvmsi elygtl ely z 700m s211.png
S211 ifless profile.png
PIBU
Cvmsi default PIBU.png
Cvmsi elygtl ely z 700m PIBU.png

These are for sites inside of the CVM-S4.26 basins:

Site No GTL 700m GTL Smaller value
s117
Cvmsi default s117.png
Cvmsi elygtl ely z 700m s117.png
S117 ifless profile.png
USC
Cvmsi default USC.png
Cvmsi elygtl ely z 700m USC.png
USC ifless profile.png
WNGC
Cvmsi default WNGC.png
Cvmsi elygtl ely z 700m WNGC.png
WNGC ifless profile.png
PEDL
Cvmsi default PEDL.png
Cvmsi elygtl ely z 700m PEDL.png
PEDL ifless profile.png
SBSM
Cvmsi default SBSM.png
Cvmsi elygtl ely z 700m SBSM.png
SBSM ifless profile.png
SVD
Cvmsi default SVD.png
Cvmsi elygtl ely z 700m SVD.png
SVD ifless profile.png

Proposed Algorithm

Our proposed algorithm for generating the velocity model is as follows:

  1. Set the surface mesh point to a depth of 25m.
  2. Query the CVM-S4.26.M01 model ('cvmsi' string in UCVM) for each grid point.
  3. Calculate the Ely taper at that point using 700m as the transition depth.
  4. Compare the values before and after the taper modification; at each grid point down to the transition depth, use the value from the method with the lower Vs value.
  5. Check values for Vp/Vs ratio, minimum Vs, Inf/NaNs, etc.

Cross-sections

Below are cross-sections of the TEST site velocity model at depths down to 600m for CVM-S4.26.M01, the taper to 700m, the lesser of the two values, and the % difference.

Note that the top two slices use a different color scale.

Depth CVM-S4.26.M01 Ely taper to 700m Selecting smaller value % difference, smaller value vs S4.26.M01
0m (queried at 25m depth)
TEST none horiz z0.png
TEST all horiz z0.png
TEST ifless horiz z0.png
TEST percentdiff horiz z0.png
100m
TEST none horiz z1.png
TEST all horiz z1.png
TEST ifless horiz z1.png
TEST percentdiff horiz z1.png
200m
TEST none horiz z2.png
TEST all horiz z2.png
TEST ifless horiz z2.png
TEST percentdiff horiz z2.png
300m
TEST none horiz z3.png
TEST all horiz z3.png
TEST ifless horiz z3.png
TEST percentdiff horiz z3.png
400m
TEST none horiz z4.png
TEST all horiz z4.png
TEST ifless horiz z4.png
TEST percentdiff horiz z4.png
500m
TEST none horiz z5.png
TEST all horiz z5.png
TEST ifless horiz z5.png
TEST percentdiff horiz z5.png
600m
TEST none horiz z6.png
TEST all horiz z6.png
TEST ifless horiz z6.png
TEST percentdiff horiz z6.png

Implementation details

To support the Ely taper approach where the smaller value is selected, the following algorithmic changes were made to the CyberShake mesh generation code. Since the UCVM C API doesn't support removing models, we couldn't just add the 'elygtl' model - it would then be included in every query, and we need to run queries with and without it to make the comparison. We also must include the Ely interpolator, since all that querying the elygtl model does is populates the gtl part of the properties with the Vs30 value, and it's the interpolator which takes this and the crustal model info and generates the taper.

  • The decomposition is done by either X-parallel or Y-parallel stripes, which have a constant depth. Check the depth to see if it is shallower than the transition depth.
  • If so, initialize the elygtl model using ucvm_elygtl_model_init(), if uninitialized. Set the id to UCVM_MAX_MODELS-1. There's no way to get model id info from UCVM, so we use UCVM_MAX_MODELS-1 as it is 29, we are very unlikely to load 29 models, and therefore unlikely to have an id conflict.
  • Change the depth value of the points to query to the transition depth. This is because we need to know the crustal model Vs value at the transition depth, so that the Ely interpolator can match it.
  • Query the crustal model again, with the modified depths.
  • Modify the 'domain' parameter in the properties data structure to UCVM_DOMAIN_INTERP, to indicate that we will be using an interpolator.
  • Change the depth value of the points to query back to the correct depth, so that the interpolator can work correctly on them.
  • Query the elygtl using ucvm_elygtl_model_query() and the correct depth.
  • Call the interpolator for each point independently, using the correct depth.
  • For each point, choose to use either the original crustal data or the Ely taper data, depending on which has the lower Vs.

In the future we plan for this approach to be implemented in UCVM, and we can simplify the CyberShake query code.

High-frequency codes

For this study, we will use the Graves & Pitarka high frequency module (hb_high) from the Broadband Platform v22.4, hb_high_v6.0.5. We will use the following parameters. Parameters in bold have been changed for this study.

Parameter Value
stress_average 50
rayset 2,1,2
siteamp 1
nbu 4 (not used)
ifft 0 (not used)
flol 0.02 (not used)
fhil 19.9 (not used)
irand Seed used for generating SRF
tlen Seismogram length, in sec
dt 0.01
fmax 10 (not used)
kappa 0.04
qfexp 0.6
mean_rvfac 0.775
range_rvfac 0.1
rvfac Calculated using BBP hfsims_cfg.py code
shal_rvfac 0.6
deep_rvfac 0.6
czero 2
c_alpha -99
sm -1
vr -1
vsmoho 999.9
nlskip -99
vpsig 0
vshsig 0
rhosig 0
qssig 0
icflag 1
velname -1
fa_sig1 0
fa_sig2 0
rvsig1 0.1
ipdur_model 11
ispar_adjust 1
targ_mag -1
fault_area -1
default_c0 57
default_c1 34

Spectral Content around 1 Hz

We investigated the spectral content of the Broadband CyberShake results in the 0.5-3 second range, to look for any discontinuities.

The plot below is from WNGC, Study 15.12 (run ID 4293).

Spectral plot for WNGC from Study 15.12, target of 0.3676g @ 3 sec. Mean is in red.

Below is a plot of the hypocenters from the 706 rupture variations which meet the target.

WNGC run4293 target event hypos.png

These events have a different distribution than the rupture variations as a whole.

Fault Percent of target RVs Percent of all RVs
San Andreas 60 44
Elsinore 21 9
San Jacinto 13 8
Other 6 39

Additionally, 88% of the selected events have a magnitude greater than the average for their source. 4% are average, and 8% are lower.

Below is a spectral plot but which includes all rupture variations and the overall mean (in orange).

Spectral plot for WNGC from Study 15.12, all variations.

Additional Sites

We created spectral plots for 7 additional sites (STNI, SBSM, PAS, LGU, LBP, ALP, PLS), located here:

Additional spectral plot sites.png
STNI SBSM PAS LGU LBP ALP PLS
STNI run4285 full spectra.png
SBSM run4291 full spectra.png
PAS run4282 full spectra.png
LGU run4321 full spectra.png
LBP run4317 full spectra.png
ALP run4298 full spectra.png
PLS run4370 full spectra.png

Verification

Updates and Enhancements

Output Data Products

Computational and Data Estimates

Lessons Learned

Stress Test

Performance Metrics

Production Checklist

Science to-dos

  • Perform validation for Northridge, Chino Hills, Whittier, Landers, Hector Mine, and North Palm Springs
  • For each validation event, calculate BBP results, CS results, and CS results with BBP Vs30 values
  • Check for spectral discontinuities around 1 Hz
  • Decide if we should stick with rvfrac=0.8 or allow it to vary
  • Determine appropriate SGT, low-frequency, and high-frequency seismogram durations
  • Update high-frequency Vs30 to use released Thompson values

Technical to-dos

  • Integrate refactoring of BBP codes into latest BBP release
  • Switch to using github repo version of CyberShake on Summit
  • Update to latest UCVM (v22.7)
  • Switch to optimized version of rupture generator
  • Test DirectSynth code with fixed memory leak from Frontera
  • Switch to using Pegasus-supported interface to Globus transfers
  • Test bundled glide-in jobs for SGT and DirectSynth jobs

Presentations, Posters, and Papers