Help in modal analysis

[waleedations]

Highly appreciate your help if you simply learn me the defference between the three analysis modes ( modal , seismic and seimic pseudo mode) and one i use each one of them especially that we done have these options in CSI Etabs for example

also i need to know which method of the eign problem solution methods match the ritz vectors and when i must use specific method ?

many thanks in advance 

[Rafal.Gaweda]

http://docs.autodesk.com/RSAPRO/2014/ENU/filesROBOT/GUID-AD28B8C7-F614-4A51-9A8B-2E1FA66D13F6.htm

http://docs.autodesk.com/RSAPRO/2014/ENU/filesROBOT/GUID-3400C9A4-F47F-4A7F-9B67-66BEE7B9105A.htm

psedomodal -> Laczos algorithm using ritz vectors
http://docs.autodesk.com/RSAPRO/2014/ENU/filesROBOT/GUID-1018E73B-377B-4827-9524-079B52409D25.htm