read_sac.zip_sac文件_shakexh2_地震台站_简洁高效_读取SAC文件的代码

%RSAC Read SAC binary files. % RSAC('sacfile') reads in a SAC (seismic analysis code) binary % format file into a 3-column vector. % Column 1 contains time values. % Column 2 contains amplitude values. % Column 3 contains all SAC header information. % Default byte order is big-endian. M-file can be set to default % little-endian byte order. % % usage: output = rsac('sacfile') % % Examples: % % KATH = rsac('KATH.R'); % plot(KATH(:,1),KATH(:,2)) % % [SQRL, AAK] = rsac('SQRL.R','AAK.R'); % % by Michael Thorne (4/2004) mthorne@asu.edu function [varargout] = rsac_little(varargin); for nrecs = 1:nargin sacfile = varargin{nrecs}; %--------------------------------------------------------------------------- % Default byte-order % endian = 'big-endian' byte order (e.g., UNIX) % = 'little-endian' byte order (e.g., LINUX) %endian = 'big-endian'; endian='little-endian'; if strcmp(endian,'big-endian') fid = fopen(sacfile,'r','ieee-be'); elseif strcmp(endian,'little-endian') fid = fopen(sacfile,'r','ieee-le'); end % read in single precision real header variables: %--------------------------------------------------------------------------- for i=1:70 h(i) = fread(fid,1,'single'); end % read in single precision integer header variables: %--------------------------------------------------------------------------- for i=71:105 h(i) = fread(fid,1,'int32'); end % Check header version = 6 and issue warning %--------------------------------------------------------------------------- % If the header version is not NVHDR == 6 then the sacfile is likely of the % opposite byte order. This will give h(77) some ridiculously large % number. NVHDR can also be 4 or 5. In this case it is an old SAC file % and rsac cannot read this file in. To correct, read the SAC file into % the newest verson of SAC and w over. % if (h(77) == 4 | h(77) == 5) message = strcat('NVHDR = 4 or 5. File: "',sacfile,'" may be from an old version of SAC.'); error(message) elseif h(77) ~= 6 message = strcat('Current rsac byte order: "',endian,'". File: "',sacfile,'" may be of opposite byte-order.'); error(message) end % read in logical header variables %--------------------------------------------------------------------------- for i=106:110 h(i) = fread(fid,1,'int32'); end % read in character header variables %--------------------------------------------------------------------------- for i=111:302 h(i) = (fread(fid,1,'char'))'; end % read in amplitudes %--------------------------------------------------------------------------- YARRAY = fread(fid,'single'); if h(106) == 1 XARRAY = (linspace(h(6),h(7),h(80)))'; else error('LEVEN must = 1; SAC file not evenly spaced') end % add header signature for testing files for SAC format %--------------------------------------------------------------------------- h(303) = 77; h(304) = 73; h(305) = 75; h(306) = 69; % arrange output files %--------------------------------------------------------------------------- OUTPUT(:,1) = XARRAY; OUTPUT(:,2) = YARRAY; %OUTPUT(1:306,3) = h(1:306)'; %pad xarray and yarray with NaN if smaller than header field if h(80) < 306 OUTPUT((h(80)+1):306,1) = NaN; OUTPUT((h(80)+1):306,2) = NaN; end fclose(fid); varargout{nrecs} = OUTPUT; end