Try to read this webpage

http://geophysics.eas.gatech.edu/people/zpeng/Teaching/SAC_Tutorial/#part2_6

Use this toolbox

http://geophysics.eas.gatech.edu/people/zpeng/Teaching/MatSAC.tar.gz

As you could see in the header I follow some interesting procedures including GATECH, I have an email response that maybe my files .sac are not in the sac format.

You can use an interactive software proposed by Philippe Lesage from Université de Savoie. Here is the reference:

Lesage, P. (2009). An interactive MATLAB software for the analysis of

seismic volcanic signals. Computers and Geosciences, 35 (10), 2137-2144.

You can contact him in order to get the software.

You can use "fopen" with "l" option for "little endian" data or "b" option for "big endian" data. Afterwards, you read 70 float number with "fread" command, 40 integer, and 23 *char (the 2° is 16 bit, others are 8 bit). Finally you read the waveforms with "fread(fid,inf,'float32')".

Use this matlab code ...

Rename your data file like 1.SAC, 2.SAC..etc.. Lets u say u hv 10 data set ..so rename last data file as 10.SAC.. to run 10 data simultaneously use the following script 

for i=1:10

num = num2str(i);

sei(i,1) = rdsac(strcat(num,'.SAC'));

end

how to convert sac file to mat file?? please help me.