### How can i calculate the theoretical effective phase velocity

Posted: **Mon Jan 09, 2012 10:52 am**

by **piero_goku**

Hi admin,

can i calculate the theoretical effective phase velocity by a modal superposition of the rayleigh modes?

Where is the file or function that can i use?

Thanks a lot.

### Re: How can i calculate the theoretical effective phase velo

Posted: **Wed Jan 18, 2012 4:26 pm**

by **admin**

The effective phase velocity depends upon the source that excites the structure, also the array used for recording has its own role. A large aperture array will separate modes whilst a small one will merge them without being able to achieve any separation. Physically, the effective phase velocity does not exist. In the ground several modes propagate at their own distinct velocities ignoring other modes. To summarize, there is no straight forward way to compute an effective velocity when several modes are simultaneously present in a wavefield. We can make some assumptions like Picozzi et al 2005 for instance, but he neglected the effect of the imperfections of our finite arrays (finite number of stations). So in Geopsy, we do not compute such effective velocity and I have no function to provide.