Difference between revisions of "CyberShake volume rotation"

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== ERF 36 Mojave 1D test ==
 
== ERF 36 Mojave 1D test ==
  
−
We repeated the above test again, but this time using the Mojave 1D model from the BBP, which has much lower near-surface velocities than the Hadley-Kanamori 1D model.
+
We repeated the above test again, but this time using the Mojave 1D model from the BBP, which has much lower near-surface velocities than the Hadley-Kanamori 1D model.  Run 7060 was done with -30 degrees, and run 7061 with -55 degrees.
  
 
{|
 
{|
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|}
 
|}
  
−
Here are statistics on the above runs:
+
Here are statistics on the above runs, for 3 sec RotD50:
  
 
{| border="1" cellpadding="2"
 
{| border="1" cellpadding="2"
−
! !! Differences (run 7057 - run 7056)<br>of linear values (cm/s2) !! Differences of natural log values !! Linear Ratios (run 7057/run 7056)
+
! !! Differences (run 7060 - run 7061)<br>of linear values (cm/s2) !! Differences of natural log values !! Linear Ratios (run 7060/run 7061)
 
|-
 
|-
 
! Min
 
! Min
−
|  
+
| -48.872131 || -0.27381 || 0.760476
 
|-
 
|-
 
! Max
 
! Max
−
|  
+
| 39.215027 || 0.273622 ||1.314718
 
|-
 
|-
 
! Mean
 
! Mean
−
|  
+
| 0.223698 || 0.004606 || 1.004685
 
|-
 
|-
 
! Std Dev
 
! Std Dev
−
|  
+
| 1.021811 || 0.011675 || 0.011753
 
|-
 
|-
 
! Mean Abs
 
! Mean Abs
−
|  
+
| 0.483368 || 0.009155
 
|}
 
|}
  
−
Here are plots comparing the difference and ratios to shortest site-rupture distance and magnitude.
+
Here are plots comparing the difference and ratios to shortest site-rupture distance and magnitude at 3 sec.
  
 
{|
 
{|
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|}
 
|}
  
−
We extracted seismograms for the biggest difference and biggest ratio, below.
+
We extracted seismograms for the biggest difference at 3 sec (48.9 cm/s2, for source 244, rupture 12, rup var 31) and biggest ratio (1.3, for source 125, rupture 234, rup var 34), below.  The Garlock fault is about 50 km from the 30 degree volume boundary, and about 40 km from the 55 degree volume boundary, so the late differences in the Garlock seismograms may be due to boundary effects.  However, the amplitude of these waves is very small - less than 1 cm/s.
  
 
{|
 
{|
 +
! Biggest difference (M7.25 Puente Hills) !! Biggest ratio (M7.05 Garlock)
 +
|-
 +
| [[File:7060_v_7061_s244_r12_v31.png|thumb|400px]]
 +
| [[File:7060_v_7061_s125_r234_v34.png|thumb|400px]]
 +
|}
 +
 +
=== Boundary effects ===
 +
 +
To test the theory that the difference we see in the Garlock seismograms is due to boundary effects, we recalculated results for the above Garlock event, but with volumes which extended an extra ~100km to the northeast, moving the fault more than 140 km away from a boundary.
 +
 +
The two seismograms with different angles show much better agreement when not near the boundary.
 +
 +
{|
 +
| [[File:s125_r234_v34_ext_vol_compare.png|thumb|600px]]
 +
|}
 +
 +
When compared to the seismograms near the boundary with the normal-sized volume, these new results are different from both:
 +
 +
{|
 +
| [[File:s125_r234_v34_vol_rot_compare.png|thumb|600px]]
 +
|}
 +
 +
=== Sponge zone tests ===
 +
 +
We realized the sponge zone widths were only 20 points, so we tried rerunning with different values.
 +
 +
With 50 and 80 points, we still see differences in the seismograms from the ones 100km+ from the volume boundary:
  
 +
{|
 +
| [[File:sponge_zone_30deg_s125_r234_v34_compare.png|thumb|600px]]
 +
|-
 +
| [[File:sponge_zone_s125_r234_v34_compare.png|thumb|600px]]
 
|}
 
|}
 +
 +
Here's a comparison of the RotD spectral plots for the 30 deg rotation, for various sponge values:
 +
 +
{|
 +
| [[File:sponge_zone_30deg_rotd_s125_r234_v34_compare.png|thumb|600px]]
 +
|}
 +
 +
Since there is no clear winner, we have decided to move ahead with '''50 points''' as a balance between reducing reflections and losing energy.

Latest revision as of 20:18, 10 February 2020

This page documents the differences we see in results when using volumes with different rotation angles, and the investigation of these differences.

Problem description

When attempting to replicate on Summit results for site USC using ERF 51 (an RSQSim-based ERF) originally obtained on Blue Waters, we ran into some difficulty.

The plot below shows a comparison of RotD values obtained on Summit (Run ID 7054) vs on Blue Waters (Run ID 7014). As you can see, there is a general trend but more scatter than anticipated; the two results should match almost exactly.

Erf51 rotd comparison.png

As a point of comparison, here are the same plots for the USC ERF 36 verification runs:

Erf36 rotd comparison.png

In particular, we identified source 684, rupture 323 as an event to investigate further. At a frequency of 3 seconds, the values obtained on Blue Waters were almost twice as big as those on Summit, 0.23 cm/s2 vs 0.12 cm/s2.

Below are plots comparing the seismograms and the geometric mean PSA values for these events on the two systems. The seismograms start to diverge after about 45 sec, and the geometric mean PSA values show the largest difference at about 3 sec.

Erf51 s684 r323 seis compare.png
Erf51 s684 r323 psa compare.png

Rotation angle

After running a series of tests, we identified that the difference seems to be related to the rotation angle: the smaller values are produced when running with a rotation angle of -55 degrees (what we have used in the past for southern California sites), and the larger values with a rotation of -30 degrees. Neither the site nor this source are near the volume boundaries.

Study 18.8 vs Study 17.3 comparison

Below are Rotd comparison plots for sites s845 and s835, hard rock sites which were included in both studies.

1D test, RWG

Rob Graves ran a 1D test in which seismograms were computed about 16 km from the source for rotation angles of 0 and -50 degrees. Below are plots comparing the three components at a variety of depths.

depth seismograms
100m
Erf51 1D RWG SGT test d0.10.png
200m
Erf51 1D RWG SGT test d0.20.png
500m
Erf51 1D RWG SGT test d0.50.png
1km
Erf51 1D RWG SGT test d1.00.png
2km
Erf51 1D RWG SGT test d2.00.png
5km
Erf51 1D RWG SGT test d5.00.png

1D test, AWP

We configured a similar test (point source, variety of depths, about 16 km from site) using the AWP SGT code and the Hadley-Kanamori 1D model. We see small differences with this code as well.

depth seismograms
100m
Erf51 1D AWP SGT test d0.10.png
200m
Erf51 1D AWP SGT test d0.20.png
500m
Erf51 1D AWP SGT test d0.50.png
1km
Erf51 1D AWP SGT test d1.00.png
2km
Erf51 1D AWP SGT test d2.00.png
5km
Erf51 1D AWP SGT test d5.00.png

1D test, AWP, Mojave 1D model

We repeated the above test using the BBP Mojave 1D model, the same model Rob used for his tests, and got much more similar results to Rob.

depth seismograms
100m
Erf51 1D AWP SGT test mojave d0.10.png
200m
Erf51 1D AWP SGT test mojave d0.20.png
500m
Erf51 1D AWP SGT test mojave d0.50.png
1km
Erf51 1D AWP SGT test mojave d1.00.png
2km
Erf51 1D AWP SGT test mojave d2.00.png
5km
Erf51 1D AWP SGT test mojave d5.00.png

ERF 36 (UCERF2, 200m spacing) test

We ran site USC using CVM-S4.26.M01 with -30 degree rotation, and compared the results to the 'standard' Southern California rotation of -55 degrees.

Overall, the differences get smaller as the ground motions get larger, and the hazard curves are visually identical, suggesting that the rotation angle has a negligible effect on hazard for UCERF2 simulations.

3 sec 5 sec 10 sec
RotD comparisons
Erf36 7052 v 7055 rotd comparison 3sec.png
Erf36 7052 v 7055 rotd comparison 5sec.png
Erf36 7052 v 7055 rotd comparison 10sec.png
Hazard curves
Erf36 7052 v 7055 comparison 3sec.png
Erf36 7052 v 7055 comparison 5sec.png
Erf36 7052 v 7055 comparison 10sec.png

Note that the dropoff off the black curve in the 3 sec plot after 1 g is due to the fact that the black and blue curves are sampled at different X-values.

ERF 36 1D test

We repeated the above test, but using the UCVM built-in SCEC 1D velocity model. These results show slightly less scatter than the 3D results, but it's more asymmetric. Note that run 7056 (the X-axis) was done with a volume rotated -55 degrees, and 7057 with -30 degrees.

3 sec 5 sec 10 sec
RotD comparisons
Erf36 7056 v 7057 rotd comparison 3sec.png
Erf36 7056 v 7057 rotd comparison 5sec.png
Erf36 7056 v 7057 rotd comparison 10sec.png

Here are statistics on the above runs:

Differences (run 7057 - run 7056)
of linear values (cm/s2)		 Differences of natural log values Linear Ratios (run 7057/run 7056)
Min -12.929062 -0.170983 0.842836
Max 12.866089 0.591074 1.805926
Mean 0.031936 0.001222 1.001283
Std Dev 0.363081 0.010961 0.011117
Mean Abs 0.193350 0.007560

We also created plots comparing the difference and ratios to shortest site-rupture distance and magnitude.

Difference (cm/s2) Ratio
Magnitude
7056 v 7057 diff mag 3sec.png
7056 v 7057 ratio mag 3sec.png
Distance
7056 v 7057 diff dist 3sec.png
7056 v 7057 ratio dist 3sec.png

ERF 36 Mojave 1D test

We repeated the above test again, but this time using the Mojave 1D model from the BBP, which has much lower near-surface velocities than the Hadley-Kanamori 1D model. Run 7060 was done with -30 degrees, and run 7061 with -55 degrees.

3 sec 5 sec 10 sec
RotD comparisons
7060 v 7061 rotd comparison 3sec.png
7060 v 7061 rotd comparison 5sec.png
7060 v 7061 rotd comparison 10sec.png

Here are statistics on the above runs, for 3 sec RotD50:

Differences (run 7060 - run 7061)
of linear values (cm/s2)		 Differences of natural log values Linear Ratios (run 7060/run 7061)
Min -48.872131 -0.27381 0.760476
Max 39.215027 0.273622 1.314718
Mean 0.223698 0.004606 1.004685
Std Dev 1.021811 0.011675 0.011753
Mean Abs 0.483368 0.009155

Here are plots comparing the difference and ratios to shortest site-rupture distance and magnitude at 3 sec.

Difference (cm/s2) Ratio
Magnitude
7060 v 7061 diff mag 3sec.png
7060 v 7061 ratio mag 3sec.png
Distance
7060 v 7061 diff dist 3sec.png
7060 v 7061 ratio dist 3sec.png

We extracted seismograms for the biggest difference at 3 sec (48.9 cm/s2, for source 244, rupture 12, rup var 31) and biggest ratio (1.3, for source 125, rupture 234, rup var 34), below. The Garlock fault is about 50 km from the 30 degree volume boundary, and about 40 km from the 55 degree volume boundary, so the late differences in the Garlock seismograms may be due to boundary effects. However, the amplitude of these waves is very small - less than 1 cm/s.

Biggest difference (M7.25 Puente Hills) Biggest ratio (M7.05 Garlock)
7060 v 7061 s244 r12 v31.png
7060 v 7061 s125 r234 v34.png

Boundary effects

To test the theory that the difference we see in the Garlock seismograms is due to boundary effects, we recalculated results for the above Garlock event, but with volumes which extended an extra ~100km to the northeast, moving the fault more than 140 km away from a boundary.

The two seismograms with different angles show much better agreement when not near the boundary.

S125 r234 v34 ext vol compare.png

When compared to the seismograms near the boundary with the normal-sized volume, these new results are different from both:

S125 r234 v34 vol rot compare.png

Sponge zone tests

We realized the sponge zone widths were only 20 points, so we tried rerunning with different values.

With 50 and 80 points, we still see differences in the seismograms from the ones 100km+ from the volume boundary:

Sponge zone 30deg s125 r234 v34 compare.png
Sponge zone s125 r234 v34 compare.png

Here's a comparison of the RotD spectral plots for the 30 deg rotation, for various sponge values:

Sponge zone 30deg rotd s125 r234 v34 compare.png

Since there is no clear winner, we have decided to move ahead with 50 points as a balance between reducing reflections and losing energy.

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