UCVM Vs30
Contents
Introduction
There may be an issue with how UCVM calculates Vs30 values. Presently UCVM uses the following formula:
- sum(Vs sampled from [0,30] at 1 meters, for 31 total values) / 31
Rob has suggested that the correct formula should be:
- 30 / sum(1 / (Vs sampled from [0, 30) at 1 meters, for 30 total values))
This can have a significant impact for Vs30 calculations. For the BBP1D model, UCVM calculates the Vs30 as 932m/s, whereas Rob's formula calculates it as 862m/s.
Another approach was used in CyberShake Study 15.12, in conversations with Rob:
- Vs30 = 30 / Sum (1/(Vs sampled from [0.5,29.5] in 1 meter increments, for 30 total values)).
Points for comparison
We have selected 6 points to compare Vs30 as generated using the CyberShake approach (using half-meters) to other UCVM approaches.
- Input points for ucvm_query:
-118.1712 34.1484 -118.1250 34.5570 -118.2860 34.0192 -118.9192 34.6402 -120.3602 36.1397 -119.2285 34.2667
| lat | lon | Velocity model | CyberShake-generated Vs30 | UCVM 18.5 Vs30 from Model | UCVM Vs30 etree.map |
|---|---|---|---|---|---|
| 34.148426 | -118.17119 | CVM-S4.26.M01 | 838.8 | 821.328 | 748.00 |
| 34.557 | -118.125 | CVM-S4.26.M01 | 2573.6 | 2573.634 | 497.68 |
| 34.0192 | -118.286 | CVM-S4.26.M01 | 313.1 | 310.574 | 280.0 |
| 34.64021 | -118.91919 | CCA-06 | 3393.9 | 3331.251 | 748.0 |
| 36.13968 | -120.36015 | CCA-06 | 2277.2 | 2279.326 | 349.0 |
| 34.26667 | -119.22848 | CCA-06 | 902.3 | 902.013 | 280.0 |
Querying cs173 is very slow due to the fine resoultion
To run on max memory on hpc cluster nodes
#!/bin/bash #SBATCH -p scec #SBATCH --ntasks=1 #number of tasks with one per processor #SBATCH -N 1 # number of nodes #SBATCH --mem 0 # Set to unlimited memory #SBATCH --time=12:00:00 #SBATCH -o ucvm2mesh_mpi_%A.out #SBATCH -e ucvm2mesh_mpi_%A.err #SBATCH --export=NONE #SBATCH --mail-user=maechlin@usc.edu #SBATCH --mail-type=END cd /auto/scec-00/maechlin/ucvmc185/utilities srun -v --mpi=pmi2 /auto/scec-00/maechlin/ucvmc185/utilities/plot_vs30_map.py -b 30.5,-126.0 -u 42.5,-112.5 -s 0.01 -a s -c cs173 -o vs30_cs173.png -bash-4.2$
== Related Links: Plot command used to plot_vs30_map. ./plot_vs30_map.py -b 30.5,-126.0 -u 42.5,-112.5 -s 0.05 -a s -c cs173 -o vs30_cs173.png
Scott posted vs30 values from CyberShake here: http://scec.usc.edu/scecpedia/CyberShake_Study_15.12#Vs_values_v2.0
Example Image:
