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SPECFEM / specfem3d

SPECFEM3D_Cartesian simulates acoustic (fluid), elastic (solid), coupled acoustic/elastic, poroelastic or seismic wave propagation in any type of conforming mesh of hexahedra (structured or not).
GNU General Public License v3.0
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Force unit using FORCESOLUTION and USE_EXTERNAL_SOURCE_FILE #1505

Closed eikmeier-cn closed 2 years ago

eikmeier-cn commented 2 years ago

Hello everybody.

When I use an external displacement source file, with unit in meters, the forces inputted in the modeling are the values in the file times the "factor force source" (FORCESOLUTION)? And is Newton the force unit?

danielpeter commented 2 years ago

yes, that's correct.

for point sources (Par_file parameter USE_FORCE_POINT_SOURCE set to .true.), the source is specified in the FORCESOLUTION file, for example with an amplitude factor such as:

factor force source:             1.d10

this factor is always added to the source, also in case an external source time function is used. the source strength refers in general to Newton [N].

however, the code is mostly unaware of units. that is, the user has to make sure the input dimensions are coherent. usually, the code assumes SI standard units (for mesh node positions given in meters, velocities in meter/seconds, etc.). still, as a user you could for example specify your mesh dimensions to be in nanometers [nm], velocities in [km/h], and then the source unit becomes less obvious.

eikmeier-cn commented 2 years ago

Thank you @danielpeter.