CyberShake Study 15.12

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CyberShake Study 15.10 takes the deterministic results from CyberShake Study 15.4 and adds broadband components.


Initial tests

We performed initial tests by using the Graves code from the current version of the BBP to synthesize stochastic seismograms, along with applying site amplification from CB2014. We used the Vs30 value taken from the same velocity model as the deterministic seismograms (CVM-S 4.26). We also applied site amplification from CB2014 to the deterministic seismograms. Then the deterministic seismograms were low-pass filtered at 1.0 Hz, and the stochastic seismograms were high-pass filtered at 1.0 Hz, and the results were combined. From this broadband seismogram we calculated PSA and RotD values.

Run 10 sec SA 5 sec SA 3 sec SA 2 sec SA 1 sec SA 0.5 sec SA 0.2 sec SA 0.1 sec SA
PAS, broadband (run 4266)
PAS 4266 10s SA.png
PAS 4266 5s SA.png
PAS 4266 3s SA.png
PAS 4266 2s SA.png
PAS 4266 1s SA.png
PAS 4266 0.5s SA.png
PAS 4266 0.2s SA.png
PAS 4266 0.1s SA.png
PAS, broadband (run 4266, blue) vs deterministic (run 3878, black)
PAS 4266 v 3878 10s SA.png
PAS 4266 v 3878 5s SA.png
PAS 4266 v 3878 3s SA.png
PAS 4266 v 3878 2s SA.png
PAS 4266 v 3878 1s SA.png
LADT, broadband (run 4271)
LADT 4271 10s SA.png
LADT 4271 5s SA.png
LADT 4271 3s SA.png
LADT 4271 2s SA.png
LADT 4271 1s SA.png
LADT 4271 0.5s SA.png
LADT 4271 0.2s SA.png
LADT 4271 0.1s SA.png
LADT, broadband (run 4271, blue) vs deterministic (run 3870, black)
LADT 4271 v 3870 10s SA.png
LADT 4271 v 3870 5s SA.png
LADT 4271 v 3870 3s SA.png
LADT 4271 v 3870 2s SA.png
LADT 4271 v 3870 1s SA.png

Sample Seismogram

Below is a seismogram for PAS, source 273, rupture 69, rupture variation 50, comparing the 1 Hz seismogram (blue) to the 10 Hz seismogram (green). Mostly, the 10 Hz seismogram looks sharper.

PAS s273 r69 rv50 3878v4266.png

Deterministic Site Amplification

We ran PAS and LADT with and without deterministic site amplification (using CB 2014, and Vs30 values from CVM-S4.26). Here are the results:

Run 10 sec SA 5 sec SA 3 sec SA 2 sec SA 1 sec SA 0.5 sec SA 0.2 sec SA 0.1 sec SA
PAS, site amplification (run 4266, blue) vs no deterministic site amplification (run 4270, black)
PAS 4266 v 4270 10s SA.png
PAS 4266 v 4270 5s SA.png
PAS 4266 v 4270 3s SA.png
PAS 4266 v 4270 2s SA.png
PAS 4266 v 4270 1s SA.png
PAS 4266 v 4270 0.5s SA.png
PAS 4266 v 4270 0.2s SA.png
PAS 4266 v 4270 0.1s SA.png
LADT, site amplification (run 4271, blue) vs no deterministic site amplification (run 4272, black)
LADT 4271 v 4272 10s SA.png
LADT 4271 v 4272 5s SA.png
LADT 4271 v 4272 3s SA.png
LADT 4271 v 4272 2s SA.png
LADT 4271 v 4272 1s SA.png
LADT 4271 v 4272 0.5s SA.png
LADT 4271 v 4272 0.2s SA.png
LADT 4271 v 4272 0.1s SA.png

Vs values v2.0

For the stochastic, we continued to use vref=865, and changed to Vs30 = 30 / Sum (1/(Vs sampled from [0.5,29.5] in 1 meter increments)).

For the deterministic, we switched to use vref = Vs @ Z=0 * Vs30 / Vs50 (50 is half the grid spacing of 100m).

For PAS, this means the LF vref went from 865 to 422.4, and the Vs30 went from 821.3 to 838.8.

For LADT, this means the LF vref went from 865 to 436.1, and the Vs30 went from 359.1 to 365.4.

Here are comparison curves for PAS and LADT.


Run 10 sec SA 5 sec SA 3 sec SA 2 sec SA 1 sec SA 0.5 sec SA 0.2 sec SA 0.1 sec SA
PAS, previous site amp (run 4266, blue) vs new deterministic site amp (run 4275, black)
PAS 4266 v 4275 10s SA.png
PAS 4266 v 4275 5s SA.png
PAS 4266 v 4275 3s SA.png
PAS 4266 v 4275 2s SA.png
PAS 4266 v 4275 1s SA.png
PAS 4266 v 4275 0.5s SA.png
PAS 4266 v 4275 0.2s SA.png
PAS 4266 v 4275 0.1s SA.png
LADT, previous site amp (run 4271, blue) vs new deterministic site amp (run 4276, black)
LADT 4271 v 4276 10s SA.png
LADT 4271 v 4276 5s SA.png
LADT 4271 v 4276 3s SA.png
LADT 4271 v 4276 2s SA.png
LADT 4271 v 4276 1s SA.png
LADT 4271 v 4276 0.5s SA.png
LADT 4271 v 4276 0.2s SA.png
LADT 4271 v 4276 0.1s SA.png

Vs values v3.0

We modified the vref calculation further, to:

vref_LF_eff = Vs30 * [ VsD5H / Vs5H ]

with Vs30 determined from the CVM as before (averaging over 1 meter increments). The other parameters are determined based on the grid spacing used in the calculation, given by H:

Vs5H = travel time averaged Vs computed from CVM in 1 meter increments down to a depth of 5*H VsD5H = discrete travel time averaged Vs computed from 3D velocity mesh used in the SGT calculation over the upper 5 grid points

So, for H=100m Vs5H would be:

Vs500 = 500 / ( Sum ( 1 / Vs sampled from [0.5,499.5] in 1 meter increments ))

And then VsD5H is given by:

VsD500 = 5/{ 0.5/Vs(Z=0m) + 1/Vs(Z=100m) + 1/Vs(Z=200m) + 1/Vs(Z=300m) + 1/Vs(Z=400m) + 0.5/Vs(Z=500m) }


This gives vref = 705 for PAS, 361 for LADT, and 294 for STNI.


Run 10 sec SA 5 sec SA 3 sec SA 2 sec SA 1 sec SA 0.5 sec SA 0.2 sec SA 0.1 sec SA
PAS, V1.0 site amp (run 4266, blue) vs V3.0 deterministic site amp (run 4279, black)
PAS 4266 v 4279 10s SA.png
PAS 4266 v 4279 5s SA.png
PAS 4266 v 4279 3s SA.png
PAS 4266 v 4279 2s SA.png
PAS 4266 v 4279 1s SA.png
PAS 4266 v 4279 0.5s SA.png
PAS 4266 v 4279 0.2s SA.png
PAS 4266 v 4279 0.1s SA.png
PAS, no deterministic site amp (run 4270, blue) vs V3.0 deterministic site amp (run 4279, black)
PAS 4270 v 4279 10s SA.png
PAS 4270 v 4279 5s SA.png
PAS 4270 v 4279 3s SA.png
PAS 4270 v 4279 2s SA.png
PAS 4270 v 4279 1s SA.png
PAS 4270 v 4279 0.5s SA.png
PAS 4270 v 4279 0.2s SA.png
PAS 4270 v 4279 0.1s SA.png
LADT, V1.0 site amp (run 4271, blue) vs V3.0 deterministic site amp (run 4280, black)
LADT 4271 v 4280 10s SA.png
LADT 4271 v 4280 5s SA.png
LADT 4271 v 4280 3s SA.png
LADT 4271 v 4280 2s SA.png
LADT 4271 v 4280 1s SA.png
LADT 4271 v 4280 0.5s SA.png
LADT 4271 v 4280 0.2s SA.png
LADT 4271 v 4280 0.1s SA.png
LADT, no deterministic site amp (run 4272, blue) vs V3.0 deterministic site amp (run 4280, black)
LADT 4272 v 4280 10s SA.png
LADT 4272 v 4280 5s SA.png
LADT 4272 v 4280 3s SA.png
LADT 4272 v 4280 2s SA.png
LADT 4272 v 4280 1s SA.png
LADT 4272 v 4280 0.5s SA.png
LADT 4272 v 4280 0.2s SA.png
LADT 4272 v 4280 0.1s SA.png
STNI, 1 Hz deterministic (run 3873, blue) vs V3.0 deterministic site amp (run 4281, black)
LADT 4272 v 4280 10s SA.png
LADT 4272 v 4280 5s SA.png
LADT 4272 v 4280 3s SA.png
LADT 4272 v 4280 2s SA.png
LADT 4272 v 4280 1s SA.png

srf2stoch_lite

To reduce the memory requirements of srf2stoch, Rob Graves created a new version, srf2stoch_lite, with much smaller memory requirements. The differences in hazard curves can be seen here, for PAS. Since srf2stoch is only used in the high frequency, we are only looking at high frequency curves. Blue is with srf2stoch, black is with srf2stoch_lite.

2 sec 1 sec 0.5 sec 0.2 sec 0.1 sec
Curve
PAS 4266 v 4274 2s SA.png
PAS 4266 v 4274 1s SA.png
PAS 4266 v 4274 0.5s SA.png
PAS 4266 v 4274 0.2s SA.png
PAS 4266 v 4274 0.1s SA.png
Avg absolute % diff 0.4% 1.9% 1.7% 33.9%
(skewed by 1 point;
otherwise it's 1.8%)		 2.7%
Max % diff 8.4%, at x=0.50g 29.6%, at x=1.58g 34.3%, at x=3.98g 1448.7%, at x=2.51g 68.4%, at x=2.00g
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