地球物理相关处理程序matlab工具箱.zip

function [seismic,ebcdic_header,binary_header]=read_segy_file_legacy(filename,varargin) % Function reads a SEG-Y file and outputs a seismic structure % % Written by: E. Rietsch: March 5, 2000 % Last updated: April 6, 2007: fix bug in reading of user-specified headers % % [seismic,ebcdic_header,binary_header]=read_segy_file_legacy(filename,varargin) % % INPUT (all input arguments are optional) % filename name of the file to read % if the name is omitted, empty, or a file with this name is not found % a file selector box will pop up to allow interactive file selection % varargin Variable number of arguments. Each argument is a cell array whose first % element is a keyword and whose other elements can be strings, numeric % values, or other cell arrays % Possible keywords are: % format floating point format to use; this cell array has the form % {'format',fp-format} where fp_format is one of the three strings: % 'ibm' IBM floating point format (standard and default) % 'ieee' IEEE format, big endian (Sun, SGI, etc.) % 'header' The binary header bytes 25-26 are used to determine the format % Default: {'format','header'}; % headers header values to be read from binary trace header; this cell array has % the form {'headers',{mnem1,first,bytes,units,description}, ... % {mnem2,first,bytes,units,description},...} where % "mnem1", "mnem2", ... denote header mnemonics (such as CDP, OFFSET), % "first" denotes the first byte in the binary header, % "bytes" denotes the number of bytes occupied by the mnemonic (2 or 4), % "units" denotes the units of measurement for the header value, and % "description" is a description of the header value. % Example: % {'headers',{'ILINE_NO',181,4,'n/a','CDP number'}, ... % {'OFFSET',37,4,'m','Source-receiver distance'}} % See below for a list of headers retrieved by default. % Default: {'headers',{}} % times times to output; this cell array has the form % {'times',first,last}; all samples with times between (and including) % first and last (in ms) are output. % Default: {'times',[]} i.e. all times % traces select traces to output; this cell array has the form % {'traces',criterion}; the variable "criterion" is used to % determine which traces to output. "criterion" can be an index % vector specifying the traces to output % Examples: {'traces',1:2:100} % {'traces',[2,5,7:10,22]} % Alternatively, it can be a string with a logical expression involving % trace headers such as '10 <= cdp && 100 >= cdp' % Examples: {'traces','cdp == 100 && offset > 100'} % {'traces','14000 < cdp && (14660 >= cdp || 14680 <= cdp)'}; % The variables in the logical relationships must be headers of the % data set; Use of functions "fix", "mod", and "round" are permitted; all % other function names will be interpreted as headers and likely cause an % error; the case of the headers in an expression does not matter. % Default: {'traces',[]} % ignoreshift By default this function reads byte locations 109-110 (see % header "lag" below) and applies the shift to the seismic data; % This behavior can be overwritten by setting this parameter to true; % Default: {'ignoreshift',false} % % Headers retrieved by default are (any one of these headers is removed if it turns out to % be identically zero): % ds_seqno Trace sequence number within line (1-4) % ffid Original Field record number (9-12) % o_trace_no Trace sequence number within original field record (13-16) % source Energy source point number (17-20) % cdp CDP ensemble number (21-24) % seq_cdp Trace sequence number within CDP ensemble (25-28) % trc_type Trace ID (1=live,2=dead,3=dummy,4=time break,...) (29-30) % offset Distance from source point to receiver group (37-40) % rec_elev Receiver elevation (41-44); % sou_elev Surface elevation at source (45-48) % depth Source depth below surface (49-52) % sou_h2od Water depth at source (61-64) % rec_h2od Water depth at receiver group (65-68) % sou_x X coordinate of source (73-76) % sou_y Y coordinate of source (77-80) % rec_x X coordinate of receiver (81-84) % rec_y Y coordinate of receiver (85-88) % lag Lag time between shot and recording start in ms (109-110) % (the value of lag is added to the start time of the % seismic; hence it can be used to simulate non-zero start % time of the data) % see also parameter "ignoreshift", above. % cdp_x X coordinate of CDP (181-184) % cdp_y Y coordinate of CDP (185-189) % iline_no In-line number (189-192) % xline_no Cross-line number (193-196) % The numbers in parentheses at the end of the line denote the location % of the corresponding bytes in the SEG-Y trace header % % OUTPUT % seismic Seismic structure % seismic.type 'seismic' (type of structure) % seismic.traces Array of seismic traces % seismic.first Start time of seismic (in ms) % seismic.last End time of seismic (in ms) % seismic.step Sample interval of seismic (in ms) % seismic.units Time units used (ms) % seismic headers Matrix with header mnemonics (one row % per header) % seismic.header_info Three-column cell array with header info % (one row per header) % seismic.line_number Line number (5-8) % seismic.reel_number Reel number (9-12) % seismic.cdp_fold CDP fold % seismic.traces_per_record Data traces per record (13-14) % seismic.aux_per_record Auxiliary traces per record (15-16) % seismic.history A four element cell array. The first element % is the start date/time of the program that % invoked this function; the second element is % the start date/time this function was executed; % and the last cell contains the name if the file % that was read % Example: % seismic.offset contains the offset for each trace % seismic.header_info.cdp two-element cell array {'m','Offset'} % the first element represents the units of measurement, the % second is a description of the header % % ebcdic_header EBCDIC reel header converted to ASCII % binary_header Binary reel header % % [seismic,ebcdic_header,binary_header]=read_segy_file(filename,varargin) global S4M ABORTED ABORTED=false; seismic=[]; ebcdic_header=[]; binary_header=[]; run_presets_if_needed % Set default parameters param.format='header'; param.headers={}; param.ignoreshift=false; param.times=[]; param.traces=[]; if ~isempty(varargin) param=assign_input(param,varargin); % Interpret/check input data end if strcmpi(param.format,'ieee') param.format='ieee-be'; end o_format='ieee-be'; if nargin <