View source for UCVM VS30 etree map (Wills 2015) UCVM's interpolation



>>> Below is for version before UCVM v22.7 using Wills 2015 <<<

== vs30 etree map ==

In UCVM, the extraction of vs30 & surface values from vs30 etree map(ucvm.e) base
on Wills 2015 is in src/ucvm/ucvm_map.c

UCVM's method:

 A Latlng is converted from geo to xy offset and then calculate the matching gridpoint into the etree map
 4 corners of interpolation grid plane points are extracted from etree  
 Interpolate_bilinear are called to arrive at the final surf and final vs30 values

Rob's method:
  
 Figure out the closest vs30 etree grid point and then use it

There are 2 big discrepancies in vs30 returned from UCVM and vs30 from Rob

<pre>
lon        lat          ucvm    Rob
-117.95682 33.84007     293.500 294
-117.81793 33.85332     351.900 352
-117.88693 33.88911     312.445 294 <---  A
-117.95898 33.86630     228.200 228
-117.93108 33.90853     386.600 387
-117.95576 33.93152     386.600 387
-117.80333 33.92733     385.100 385
-117.85709 33.85299     228.200 228
-118.04687 33.88925     228.200 228
-118.05753 33.92822     386.600 387
-117.86562 34.02098     419.818 352 <---  B
-117.98124 33.80772     228.200 228
-117.92242 33.87170     293.500 294
-117.92371 33.94536     385.411 385
-117.95081 34.00950     293.500 294
</pre>

Adding debug statements to UCVM to output the surf and vs30 from multiple grid points that were used

A: ucvm_query -m cvms5 -l 33.88911,-117.88693,0
<pre>
>>> grid location: x0 5648 y0 1702
>>>    corners -> 0 0
>>>    corners -> 1 0
>>>    corners -> 0 1
>>>    corners -> 1 1
>>> 4 sets of grid point values..
>>>...surf 84.540581 78.770798 79.989998 81.523117
>>>...vs30 386.600006 293.500000 385.100006 293.500000
>>>...FINAL surf 80.292620 vs30 312.445426 
 -117.8869    33.8891      0.000     80.293    312.445      cvms5   1621.082    854.413   2032.805       none      0.000      0.000      0.000      crust   1621.082    854.413   2032.805
</pre>

B:ucvm_query -m cvms5 -l 34.02098,-117.86562,0
<pre>
>>> grid location: x0 5598 y0 1746
>>>    corners -> 0 0
>>>    corners -> 1 0
>>>    corners -> 0 1
>>>    corners -> 1 1
>>> 4 sets of grid point values..
>>>...surf 207.701019 182.753067 176.160889 172.366409
>>>...vs30 468.399994 385.100006 468.399994 351.899994
>>>...FINAL surf 179.832657 vs30 419.817623 
 -117.8656    34.0210      0.000    179.833    419.818      cvms5   1714.918    943.196   2076.987       none      0.000      0.000      0.000      crust   1714.918    943.196   2076.987
</pre>

For a matching location,

ucvm_query -m cvms5 -l 33.84007,-117.95682,0
<pre>
>>> grid location: x0 5652 y0 1664
>>>    corners -> 0 0
>>>    corners -> 1 0
>>>    corners -> 0 1
>>>    corners -> 1 1
>>> 4 sets of grid point values..
>>>...surf 34.806599 34.438507 37.543068 34.159943
>>>...vs30 293.500000 293.500000 293.500000 293.500000
>>>...FINAL surf 34.435791 vs30 293.500000 
 -117.9568    33.8401      0.000     34.436    293.500      cvms5   1626.430    833.127   2021.462       none      0.000      0.000      0.000      crust   1626.430    833.127   2021.462
</pre>

[https://g-c662a6.a78b8.36fe.data.globus.org/scecpedia/ucvm/vs30_etree_map/vs30_etree_map_wills2015.tar.gz raw data]

== Related Links ==
*[[Wills_Map]]
*[[UCVM]]