HighF La Habra Verification

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This page documents the High-F activities and decisions for the 2020 verification runs for four groups: Olsen et al. (AWP), Graves (RWG) and Taborda, Restrepo et al. (Hercules), Breuer (Edge). Verification of 5 Hz time series (4Hz PSA, multiple bands verification) using La Habra stations.


USGS Earthquake Information

Observational Data

Region Definitions

Mesh generation rules and parameter constraints

Velocities

  • 1. Set Min Vs=500 m/s
  • 2. If Vs was lower than 500 m/s and adjusted, then adjust Vp with original Vp/Vs ratio (so that we don’t have the automatic Vs/Vp of 3). We may want to set a minimum value of Vp (Rob to check)
  • 3. Then set Max Vp/Vs= 3, if lower Vp to maintain the max of 3 ratio

Lame parameters (mu and lambda)

Use mu and Lambda parameters to fix Vp/Vs issues in the CVM where necessary, as part of the mesh generation. Need to make sure that patches are physical and not only to make the codes run.

  • Rob to check if raw model produces lambda of <=zero.
  • Note: lambda of zero corresponds to Vp/Vs= sqrt(2)=1.45
  • Note: typical Vp speeds are 330 m/s in air, 1450 m/s in water and about 5000 m/s in granite

Anelastic attenuation (Q)

Frequency-independent Q definition

  • Qs=100*Vs(km/s)
  • Qp=2*Qs

Upper frequency

  • 5Hz: based on 500 m/s and 20 m spacing
  • Kim and Rob have been low-pass filtering the slip function at 5 Hz
  • Ricardo and Naeem don’t filter the source

Source Models

We discussed various sources, both point source (PS) and finite-fault (FF) in the past for our verifications and validation.

  • Also ran various smoothed variations of the GP15 FF (need to find a reference for that)
  • Rob to follow-up with Wei (last communication was in April 2017).

Proposed models for verification and validation:

  • PS: model from En-Jui (moment tensor). Can we replicate En-Jui's results? Would need to use CVMS4.26 (cms5) - not desirable. We could perform a check with CVS4.26.M01 at 5 sec. Need to use the same record En-Jui used. Proposed to use records from Figure 6 in:
    • Lee E.-J., P. Chen, and T.H. Jordan (2014). Testing Waveform Predictions of 3D Velocity Models against Two Recent Los Angeles Earthquakes. Seismol. Res. Lett., 85 (6): 1275–1284 (Paper here)
  • FF: Summary of agreed-upon FF model (gp.5.3.02)
  • FF refined with velocity model Slides from Graves presented on Feb. 21 2018

Path forward on VERIFICATION paper

Misc definitions

Domains

  • Small domain: defined here.
  • Large domain: defined here.
  • Proposed medium domain:
The four corners of medium La Habra Simulation domain are:
 c1= -118.387131  33.887287
 c2= -117.970993  34.301479
 c3= -117.472496  33.955025
 c4= -117.889359  33.542511
And the model dimensions are:
 xlen=    60.0000 km
 ylen=    60.0000 km
 zlen=    25.0000 km

Note that this is not a UTM projection. It is transverse Mercator with spherical reference and corresponds very closely to the proj4 projection: 
+proj=tmerc +lat_0=%f +lon_0=%f +ellps=sphere +a=6378139.0 +b=6378139.0 +units=m +no_defs

where lat_0, lon_0 are the domain center coordinates, which in this case are: lon= -117.930000 lat=  33.922000

The regional seismic velocity model used by all modelers is: CVMS4.26.M01 (called cvmsi in UCVM, as per Table 1 in this UCVM paper), do NOT apply a GTL to the model, but apply the rules described here.

Vs30 at recording stations

  • For interpretation of recorded data, use in order of preference
    • values listed as "Vs30 (m/s) selected for analysis" in the NGA-West2 database flatfile
    • if stations are not included in the NGA-West2 database, we will use the values from Will et al. 2015 as retrieved from UCVM (with interpolation)
  • For interpretation of simulation data
    • We retrieved the Vs30 values using UCVM v19.4 for CVM-S4.26.M01 (cvmsi), for CVM-S4.26 (to show impact of adding .M01 GTL), for CVM-S4 (to check if Vs30 matches .M01 exactly), and from the Wills 2015 Vs30 model embedded in UCVM.
  • For the Vs30_query against the models uses a slowness algorithm, and a 1 meter spacing.
  • The Wills 2015 Vs30 values are based a processing sequence that includes converting a GIS shape file into a rasterized Vs30 grid of values produced by Kevin Milner. Kevin provided a file raster_0.00025.flt, which is rasterized with 0.00025 degree spacing (~25 meters). This file is then used to generate an etree which is used to stored the rasterized data. When query points are given between grid points, then ucvm implements interplolation of Vs30 values between associated grid points. More
  • More details on the Willis Map integration here: Wills Map.
  • Descriptions of UCVM Vs30 Slowness algorithm here: UCVM_Vs30.
  • Description of CyberShake Vs30 Slowness algorithm here: CyberShake_Code_Base#Stochastic codes

Step 1: selection and verification of source model using the small domain

  • Use medium domain, with Vs floor of 500 m/s (CVMS4.26-M01 (cmvsi)) and constraints, as described here
  • We agreed that all the modelers will use a version of the medium domain that is rotated by 39.9 degrees, so as to remove a source of difference we can control. We observed different results due to rotation of the domain in CyberShake simulations a few months ago, for which we could not account for by considering the model edges and boundary effects. There seems to be some anisotropy in the model that may be due to the staggered grid.
BBP Station List
  • Focused on 15 near-by stations selected by Rob
UCVM Vs30 Values
Station Id Lat - NGA-West2 Lon - NGA-West2 Vs30 - NGA-West2 Vs30 - Wills 2015 (UCVM v19.4) Vs30 - Slowness Method (1m res) CVM-S4.26.M01 (cvmsi) (UCVM v19.4)
CE_13066 -117.9568 33.8401 288.00 293.500 284.461
CE_13849 -117.8180 33.8535 385.00 351.900 329.762
CE_13878 -117.8870 33.8891 398.00 313.585 344.043
CE_13879 -117.9591 33.8663 299.00 228.200 287.845
CE_13880 -117.9311 33.9086 324.00 386.600 349.812
CE_13881 -117.9557 33.9315 353.00 386.600 349.317
CE_13882 -117.8034 33.9274 412.00 385.100 367.423
CE_13883 -117.8578 33.8534 300.00 228.200 329.762
CE_14026 -118.0469 33.8892 281.00 228.200 287.845
CE_14027 -118.0576 33.9283 342.00 386.600 354.637
CE_23938 -117.8657 34.0209 402.00 418.980 370.670
CI_BRE -117.9812 33.8078 238.00 228.200 285.871
CI_FUL -117.9225 33.8717 309.00 293.500 362.574
CI_OLI -117.9237 33.9454 328.00 385.433 331.459
CI_WLT -117.9508 34.0095 265.00 293.500 309.646

The BBP station list was updated to include station latitude and longitude coordinates up to 4 decimal places. It includes the Vs30 from the NGA-West2 flat file, updated on May 12th, 2020. 

-117.9568 33.8401  CE_13066  288.00  0.1250  4.0000
-117.8180 33.8535  CE_13849  385.00  0.1250  4.0000
-117.8870 33.8891  CE_13878  398.00  0.1250  4.0000
-117.9591 33.8663  CE_13879  299.00  0.1250  4.0000
-117.9311 33.9086  CE_13880  324.00  0.1250  4.0000
-117.9557 33.9315  CE_13881  353.00  0.1250  4.0000
-117.8034 33.9274  CE_13882  412.00  0.1250  4.0000
-117.8578 33.8534  CE_13883  300.00  0.1250  4.0000
-118.0469 33.8892  CE_14026  281.00  0.1250  4.0000
-118.0576 33.9283  CE_14027  342.00  0.1250  4.0000
-117.8657 34.0209  CE_23938  402.00  0.1250  4.0000
-117.9812 33.8078  CI_BRE  238.00  0.1250  4.0000
-117.9225 33.8717  CI_FUL  309.00  0.1250  4.0000
-117.9237 33.9454  CI_OLI  328.00  0.1250  4.0000
-117.9508 34.0095  CI_WLT  265.00  0.1250  4.0000
Source model
  • Use RWG best source:
    • Rob ran a series of tests to select a finite source to use with the Vmod floored at 500 m/s (powerpoint here)
    • The suite of 40 SRF rupture models for the 2.5 km X 2.5 km fault are contained in this tarfile (364 MB). There are 2 resolutions: 100 m subfaults and 20m subfaults. The recommendation is to use 20m subfaults if possible.
  • Verify that best RWG source is good at 15 stations for all models. This is a first-order test for the purpose of the verification paper only, modelers can chose another source for the validation paper later, if, for example, they use another velocity model or different constraints.
  • Step 1 was completed on June 17 during our call, at which time we moved to Step 2 below. Combined results from all groups here!

Step 2: verification with the selected source, using the large domain

  • Then all modelers rerun large region
    • We agreed to keep the same rotation as for the small domain (39.9 degrees)
    • Revised station list available (here)
  • Perform verification using results and plots from
    • tsprocess time series/FAS/PSA combo plots
    • tsprocess Anderson GOF scores and maps (GMT capability needs to be restored due to updates)
    • BBP (GOF with T, distance, mapped, etc.; consider adding Vs30-based plots on BBP)
  • Compare with 1D BBP sims (with Vs30=500 for all stations, with site response)?

Step 3: write paper, publish

Related Pages

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