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SAC FORMAT  

2009-06-12 14:22:44|  分类: 数据 |  标签: |举报 |字号 订阅

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Seismic Analysis Code (SAC) format consists of a trace header followed by one or two data sections. Time series with a uniform sample interval consist of one data section containing the dependent variable (usually, but not necessarily, amplitude); time series with a variable interval include a second data section containing the idependent variable. SAC format may be either binary (most common) or alpha-numeric (or ascii).

Binary SAC

Binary SAC format contains a 158-word trace header (32 bits/word) and data sections comprised of 32-bit floating point data samples.

Alpha-numeric (ASCII) SAC

Alpha-numeric SAC format contains a 30-card (SAC is written in FORTRAN) trace header (the equivalet of the binary header) and data sections comprised of 5-sample records written as G15.7 floats.

 

Binary SAC
Bytes/Type
Alpha-numeric SAC
Card/Word/Format
Variable Name Description
1 / Float 1 / 1 / G15.7 DELTA Nominal sample interval (required)
2 / Float 1 / 2 / G15.7 DEPMIN Minimum dependent variable value
3 / Float 1 / 3 / G15.7 DEPMAX Maximum dependent variable value
4 / Float 1 / 4 / G15.7 SCALE Dependent variable scale factor (not used)
5 / Float 1 / 5 / G15.7 ODELTA Observed sample interval (if different from DELTA
6 / Float 2 / 1 / G15.7 B Beginning value of independent variable (required)
7 / Float 2 / 2 / G15.7 E Ending value of independent variable (required)
8 / Float 2 / 3 / G15.7 O Event origin time (seconds rel. to referece time)
9 / Float 2 / 4 / G15.7 A First arrival time (seconds rel. to reference time)
10 / Float 2 / 5 / G15.7 INTERNAL Internal to SAC
11-15 / Float 3 / 1-5 / G15.7 T0-4 User-defined time pick (seconds rel. to reference time)
16-20 / Float 4 / 1-5 / G15.7 T5-9 User-defined time pick (seconds rel. to reference time)
21 / Float 5 / 1 / G15.7 F End of event (seconds rel. to reference time)
22-5 / Float 5 / 2-5 / G15.7 RESP0-3 Instrument response parameters (not currently used)
26-30 / Float 6 / 1-5 / G15.7 RESP4-8 Instrument response parameters (not currently used)
31 / Float 7 / 1 / G15.7 RESP9 Instrument response parameters (not currently used)
32 / Float 7 / 2 / G15.7 STLA Station latitude (degrees, + is N, - is S)
33 / Float 7 / 3 / G15.7 STLO Station longitude (degrees, + is E, - is W)
34 / Float 7 / 4 / G15.7 STEL Station elevation (meters, not currently used)
35 / Float 7 / 5 / G15.7 STDP Station depth below surface (meters, not currently used)
36 / Float 8 / 1 / G15.7 EVLA Event latitude (degrees, + is N, - is S)
37 / Float 8 / 2 / G15.7 EVLO Event longitude (degrees, + is E, - is W)
38 / Float 8 / 3 / G15.7 EVEL Event elevation (meters, not currently used)
39 / Float 8 / 4 / G15.7 EVDP Event depth (meters, not currently used)
40 / Float 8 / 5 / G15.7 UNUSED Not currently used
41-45 / Float 9 / 1-5 / G15.7 USER0-4 User-defined variable
46-50 / Float 10 / 1-5 / G15.7 USER5-9 User-defined variable
51 / Float 11 / 1 / G15.7 DIST Station to event distance (km)
52 / Float 11 / 2 / G15.7 AZ Event to station azimuth (degrees)
53 / Float 11 / 3 / G15.7 BAZ Station to event azimuth (degrees)
54 / Float 11 / 4 / G15.7 GCARC Station to event great circle arc length (degrees)
55 / Float 11 / 5 / G15.7 INTERNAL Internal to SAC
56 / Float 12 / 1 / G15.7 INTERNAL Internal to SAC
57 / Float 12 / 2 / G15.7 DEPMEN Mean value of dependent variable
58 / Float 12 / 3 / G15.7 CMPAZ Component azimuth (degrees clockwise from N)
59 / Float 12 / 4 / G15.7 CMPINC Component incident angle (degrees from vertical)
60 / Float 12 / 5 / G15.7 UNUSED Not currently used
61-65 / Float 13 / 1-5 / G15.7 UNUSED Not currently used
66-70 / Float 14 / 1-5 / G15.7 UNUSED Not currently used
71 / Integer 15 / 1 / I10 NZYEAR GMT year corresponding to reference (zero) time
72 / Integer 15 / 2 / I10 NZJDAY GMT julian day
73 / Integer 15 / 3 / I10 NZHOUR GMT hour
74 / Integer 15 / 4 / I10 NZMIN GMT minute
75 / Integer 15 / 5 / I10 NZSEC GMT second
76 / Integer 16 / 1 / I10 NZMSEC GMT millisecond
77-79 / Integer 16 / 2-4 / I10 INTERNAL SAC internal use
80 / Integer 16 / 5 / I10 NPTS Number of points per data component (required)
81-83 / Integer 17 / 1-2 / I10 INTERNAL SAC internal use
83-85 / Integer 17 / 3-5 / I10 UNUSED Not currently used
86 / Enumeration 18 / 1 / I10 IFTYPE Type of file (required):
01 = ITIME (time series file)
02 = IRLIM (spectral file, real & imaginary)
03 = IAMPH (spectral file - amplitude & phase)
04 = IXY (general x versus y data)
IXYZ (general XYZ (3-D) file)
87 / Enumeration 18 / 2 / I10 IDEP Type or dependent variable:
05 = IUNKN (unknown)
06 = IDISP (displacement (nanometers))
07 = IVEL (velocity (nm/sec))
50 = IVOLTS (velocity (volts))
08 = IACC (acceleration (nm/sec/sec))
88 / Enumeration 18 / 3 / I10 IZTYPE Reference time equivalence:
50 = IUNKN (unknown)
09 = IB (begin time)
10 = IDAY (midnight of reference GMT day)
11 = IO (event origin time)
12 = IA (first arrival time)
13-22 = IT0-9 (user-defined time pick)
89 / Integer 18 / 4 / I10 UNUSED GMT minute
90 / Enumeration 18 / 5 / I10 IINST Type of recording instrument (not currently used)
91 / Enumeration 19 / 1 / I10 ISTREG Station geographic region (not currently used)
92 / Enumeration 19 / 2 / I10 IEVREG Event geographic region (not currently used)
93 / Enumeration 19 / 3 / I10 IEVTYP Type of event:
05 = IUNKN (unknown)
37 = INUCL (nuclear event)
38 = IPREN (nuclear pre-shot event)
39 = IPOSTN (nuclear post-shot event)
40 = IQUAKE (earthquake)
41 = IPREQ (foreshock)
42 = IPOSTQ (aftershock)
43 = ICHEM (chemical explosion)
44 = IOTHER (other)
94 / Enumeration 19 / 4 / I10 IQUAL Quality of data (not currently used):
45 = IGOOD (good data)
46 = IGLCH (glitches)
47 = IDROP (dropouts)
48 = ILOWSN (low signal to noise ration)
44 = IOTHER (other)
95 / Enumeration 19 / 5 / I10 ISYNTH Synthetic data flag (not currently used):
49 = IRLDTA (real data)
96-100 / Integer 20 / 1-5 / I10 UNUSED Not currently used
101-105 / Integer 21 / 1-5 / I10 UNUSED Not currently used
106 / Logical 22 / 1 / I10 LEVEN TRUE if data are evenly spaced (required)
107 / Logical 22 / 2 / I10 LPSPOL TRUE if station components have positive polarity (left-had rule)
108 / Logical 22 / 3 / I10 LOVROK TRUE if it is ok to overwrite this file on disk
109 / Logical 22 / 4 / I10 LCALDA TRUE if DIST, AZ, BAZ, and GCARC are to be calculated
from station and event coordinates
110 / Logical 22 / 5 / I10 UNUSED Not currently used
111-112 / Alphanumeric 23 / 1-2 / A8 KSTNM Station name
113-116 / Alphanumeric 23 / 3-6 / A16 KEVNM Event name
117-118 / Alphanumeric 24 / 1-2 / A8 KHOLE Hole identification, if nuclear event
119-120 / Alphanumeric 24 / 3-4 / A8 KO Event origin time identification
121-122 / Alphanumeric 24 / 5-6 / A8 KA First arrival time identification
123-128 / Alphanumeric 25 / 1-6 / A8 KT0-2 User-supplied time pick identification
129-134 / Alphanumeric 26 / 1-6 / A8 KT3-5 User-supplied time pick identification
135-140 / Alphanumeric 27 / 1-6 / A8 KT6-8 User-supplied time pick identification
141-142 / Alphanumeric 28 / 1-2 / A8 KT9 User-supplied time pick identification
143-144 / Alphanumeric 28 / 3-4 / A8 KF Fini identification
145-146 / Alphanumeric 28 / 5-6 / A8 KUSER0 User-defined variable
147-150 / Alphanumeric 29 / 1-4 / A8 KUSER1-2 User-defined variable
151-152 / Alphanumeric 29 / 5-6 / A8 KCMPNM Component name
153-154 / Alphanumeric 30 / 1-2 / A8 KNETWK Name of seismic network
155-156 / Alphanumeric 30 / 3-4 / A8 KDATRD Date data was read onto computer
157-158 / Alphanumeric 30 / 5-6 / A8 KINST Generic name of recording instrument
[an error occurred while processing this directive]

P-DATA FORMAT

A PASSCAL (P) data stream developed consists of a brief trace header and an XDR (a C external data representation) array of data samples. The XDR array holds the number and size of integer data samples described in the trace header. The P-data stream was designed to hold data from raw REF TEK data packets. The trace header is described below.

Bytes Type Description
1 - 4 long maximun long integer size from limit.h
5 - 8 long REF TEK channel number
9 - 12 long epoch time in seconds of first sample
13 - 16 long millisecond of first sample
17 - 20 long sample rate in Hertz
21 - 24 long size of integer data samples (2 or 4 bytes)
25 - 28 long number of samples in the following XDR data array
29 - 32 char pointer pointer to XDR data array
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