Thread: Problem with Beamforming

Dear Friends and Colleagues:

It is quite a while that I am struggling with 'BEAM' command of SAC and
still cannot get it right.

For a signal (a 5.4 Mw earthquake in central Asia: 1996/01/09, centroid.
time: 06:27) approaching YELLOWKNIFE array with bearing (azimuth) of 9.7
degrees (back-azimuth:
344.7 degrees), I ran the following command for all vertical components of
the event read into SAC:

BEAM B 344.7 V 15 EC 33 6.0 C 0. 0. 0. W beam

The velocity of 18 Km/s is what I have calculated from the P slowness of
5.9 s/deg.

The resulting 'beam' is not even so good if individual files are stacked
with zero delay. Furthermore,
it is shifted about 10 seconds to the left.

Can anyone shed some light on this? SAC manual is really not a big help on
this issue.

Thank you in advance,

Alireza