Accelerations and velocities of all mesh elements for the entire model

[xuhanqing98]

Dear all In Specfem3D, STATIONS can be added to observe the acceleration and velocity of the point, etc. I would like to ask you: Is there a way to know the acceleration and velocity of all grid cells in the entire model after the earthquake event and output it directly? Thanks！

[danielpeter]

you could try with the movie settings in Par_file to output the whole wavefield on the grid:

MOVIE_VOLUME                    = .true.
NTSTEP_BETWEEN_FRAMES           = 200

that will output the velocity wavefield by default. these files become quickly very large though.

[xuhanqing98]

@danielpeter Thank you very much for answering my question on Github, maybe my expression is not clear. The sema, semv, and semd files I get by running Specfem3D now are based on the STATIONS input in DATA. If I want to get the maximum value in the sema and other files of all mesh element nodes of the model except STATIONS, is there any way to achieve it? ?

[danielpeter]

hi Xu, regarding the maximum values for example of the sema (acceleration), that would be the PGA values you're after. there is an option in the Par_file to store these on the surface of the model as so-called shakemaps:

CREATE_SHAKEMAP                 = .true.
MOVIE_TYPE                      = 1
USE_HIGHRES_FOR_MOVIES          = .true.

this setting would output a corresponding file at the end of the simulation with the horizontal-component peak-ground values for displacement, velocity and acceleration. this can be visualized then by the xcreate_movie_shakemap_AVS_DX_GMT helper tool in the package.

if you are looking for the PGV/PGA values inside the model, then that's not implemented yet and you would have to do this work-around with putting stations wherever your area of interest would be.

hope this helps a bit to evaluate your options :)