# SW4 Mesh Development

From SCECpedia

Jump to navigationJump to searchGoal: Create NorCal CyberShake Mesh for SW4

## Contents

## Mesh Region

Region should match the SFBR model https://www.usgs.gov/programs/earthquake-hazards/science/3-d-geologic-and-seismic-velocity-models-san-francisco-bay

- ne_coord (-122.562365, 39.174505)
- nw_coord (-123.858493, 38.424179)
- sw_coord (-121.922036, 36.320331)
- se_coord (-120.644051, 37.050062)

- 140km x 290km

## Config Script

- input 4 corners (and projection) and spacing
- calc rotation angle
- distance between points
- calculate nx, ny, nz based on spacing

## Define Region

- origin
- rotation angle
- distance x
- distance y
- distance z
- spacing

## Low Res UCVM2Mesh Configuration for SFBR Model

To test our mesh formats for SW4, we will test with a low resolution

- rot=-53.9
- x0=-123.858493
- y0=38.424179
- z0=0.0
- spacing=500.0
- Dist x = 140,000
- Dist y = 290,000
- Dist z = 40,000
- nx=280
- ny=580
- nz=80

## Full Res UCVM2Mesh Configuration for SFBR Model

- rot=-53.9
- x0=-123.858493
- y0=38.424179
- z0=0.0
- spacing=25.0
- Dist x = 140,000
- Dist y = 290,000
- Dist z = 60,000
- nx=
- ny=
- nz=

## SF CVM

These are the coordinates of the detailed USGS SFBA VM:

ne_coord (-122.562365, 39.174505) nw_coord (-123.858493, 38.424179) sw_coord (-121.922036, 36.320331) se_coord (-120.644051, 37.050062)

Regarding the azimuth of the velocity model in the SFBA, we use a rotation of 143.638º, assuming an initial rectangle aligned with the geographical coordinates and anchor at the south-west corner. After applying this rotation, this point at the origin becomes the north-east corner of the domain.

can you discretize the mesh in 100 m in horizontal and 25 m in vertical, following a cube? Eventually at larger depths the discretization is coarser which will allow to same mamory, but I do not know yet how the model is defined in depth (I think at a some points the blocks are defined every 200 m in depth, but I haven't explored this feature of the velocity model).

## Example from CyberShake

We don't actually generate a ucvm2mesh config file as part of the process of creating CyberShake meshes, but I've created what I think is the correct ucvm2mesh file for USC. The rotation angle is -55 degrees, and the 4 corners should be about:

-122.46716 34.52173 (x= 0.000 y= 0.000) -119.66138 37.97316 (x= 460.000 y= 0.000) -113.59525 34.44267 (x= 460.000 y= 672.000) -116.52591 31.13175 (x= 0.000 y= 672.000)

## Sim Volume CyberShake Site s3446

- The yellow box, the volume for site s3446 - has the following specs:
- Dimensions: 460.8 x 774.4 x 50.56 km
- Rotation angle: 36 degrees counterclockwise
- Corner points:
- -126.18649, 39.75063 (W)
- -121.85281, 42.27791 (N)
- -116.72395, 36.56162 (E)
- -120.90294, 34.22243 (S)