You can use SEGYMAT or Seismiclab package. Just be careful about the endians.

Hi Naser 

Are these two packages good for 3-D data?

Regards

For 3D data Matlab is not a good option. We usually use Seismic Unix or Madagascar. in Seismic Unix you can use segyread and in Madagascar sfsegyread.

ftp://ftp.cwp.mines.edu/pub/cwpcodes/sumanual_600dpi_a4.pdf

http://www.ahay.org/wiki/Main_Page

I strongly recommend the Seislab package to work with 3D or 2D seismic data in Matlab. Use read_segy_file to read a segy file and you will have your data nicely structured for processing.

http://www.mathworks.com/matlabcentral/fileexchange/15674-seislab-3-01

%% Read in seismic data

% SegyTrace open the SEG Y file and reads the data and header information.

% Creates objects used to access trace data (trcdat), trace header (trchdr) and header definition (trcdef).

segy = SegyTrace(filein);

[trchdr,trcdat,trcdef] = segy.read;

[hdrvals,fieldnames,datatypes] = segy.struct2double(trchdr);