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alomax / NonLinLoc

Probabilistic, Non-Linear, Global-Search Earthquake Location in 3D Media
http://www.alomax.net/nlloc/docs
GNU General Public License v3.0
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3D velocity model in NonLinLoc for a spherical coordinate system #51

Open DawnChen0717 opened 1 month ago

DawnChen0717 commented 1 month ago

Dear Anthony,

How can I use a 3D grid for a spherical coordinate system? The manual only mentions how to implement in a Cartesian coordinate system.

Many thanks, Dawn

alomax commented 1 month ago

Hello Dawn,

For spherical coordinates use TRANS GLOBAL. Then the x and y, and dx and dy specifications for *GRID and LOCGRID are in degrees. See https://github.com/alomax/NonLinLoc/blob/dev/nlloc_global_sample/run/neic_global.in for some examples control file entries.

To use 3D travel-times, it is best to calculate the 3D travel-times outsize of NLL and transform to the NLL GRID format with the TRANS GLOBAL conventions above to store the travel-times. The grid file names must also follow the NLL conventions: 

my_area_3Dttime.P.<NET_STA_CODE>.time.buf
my_area_3Dttime.P.<NET_STA_CODE>.time.hdr

I am sure you need more details, but I start with just the above to be sure I am answering you question correctly.

Best regards, Anthony