# obspy.io.sac.header

SAC header specification, including documentation.

Header names, order, types, and nulls, as well as allowed enumerated values, are specified here. Header name strings, and their array order are contained in separate float, int, and string tuples. Enumerated values, and their allowed string and integer values, are in dictionaries. Header value documentation is in a dictionary, for reuse throughout the package.

Field Name | Type | Description
--- | --- | ---
a = | F | First arrival time (seconds relative to reference time.)
az = | F | Event to station azimuth (degrees).
b = | F | Beginning value of the independent variable.
baz = | F | Station to event azimuth (degrees).
cmpaz = | F | Component azimuth (degrees, clockwise from north).
cmpinc = | F | Component incident angle (degrees, from vertical).
delta = | F | Increment between evenly spaced samples (nominal value).
depmax = | F | Maximum value of dependent variable.
depmen = | F | Mean value of dependent variable.
depmin = | F | Minimum value of dependent variable.
dist = | F | Station to event distance (km).
e = | F | Ending value of the independent variable.
evdp = | F | Event depth below surface (meters).
evel = | F | Event elevation (meters).
evla = | F | Event latitude (degrees north positive).
evlo = | F | Event longitude (degrees east positive).
f = | F | Fini/end of event time (seconds relative to reference time.)
gcarc = | F | Station to event great circle arc length (degrees).
idep = | I | Type of dependent variable: IUNKN (Unknown) IDISP (Displacement in nm) IVEL (Velocity in nm/sec) IVOLTS (Velocity in volts) IACC (Acceleration in nm/sec/sec)
ievreg = | I | Event geographic region.
ievtyp = | I | Type of event: IUNKN (Unknown) INUCL (Nuclear event) IPREN (Nuclear pre-shot event) IPOSTN (Nuclear post-shot event) IQUAKE (Earthquake) IPREQ (Foreshock) IPOSTQ (Aftershock) ICHEM (Chemical explosion) IQB (Quarry or mine blast confirmed by quarry) IQB1 (Quarry/mine blast with designed shot info-ripple fired) IQB2 (Quarry/mine blast with observed shot info-ripple fired) IQMT (Quarry/mining-induced events: tremors and rockbursts) IEQ (Earthquake) IEQ1 (Earthquakes in a swarm or aftershock sequence) IEQ2 (Felt earthquake) IME (Marine explosion) IEX (Other explosion) INU (Nuclear explosion) INC (Nuclear cavity collapse) IO_ (Other source of known origin) IR (Regional event of unknown origin) IT (Teleseismic event of unknown origin) IU (Undetermined or conflicting information) IOTHER (Other)
iftype = | I | Type of file: ITIME {Time series file} IRLIM {Spectral file—real and imaginary} IAMPH {Spectral file—amplitude and phase} IXY {General x versus y data} IXYZ {General XYZ (3-D) file}
iinst = | I | Type of recording instrument.
imagsrc = | I | Source of magnitude information: INEIC (National Earthquake Information Center) IPDE (Preliminary Determination of Epicenter) IISC (International Seismological Centre) IREB (Reviewed Event Bulletin) IUSGS (US Geological Survey) IBRK (UC Berkeley) ICALTECH (California Institute of Technology) ILLNL (Lawrence Livermore National Laboratory) IEVLOC (Event Location (computer program) ) IJSOP (Joint Seismic Observation Program) IUSER (The individual using SAC2000) IUNKNOWN (unknown)
imagtyp = | I | Magnitude type: IMB (52): Bodywave Magnitude IMS (53): Surfacewave Magnitude IML (54): Local Magnitude IMW (55): Moment Magnitude IMD (56): Duration Magnitude IMX (57): User Defined Magnitude
iqual = | N | Quality of data, as integers. Enum values listed: IGOOD (45) (Good data) IGLCH (46) (Glitches) IDROP (47) (Dropouts) ILOWSN (48) (Low signal to noise ratio) IOTHER (44) (Other)
istreg = | I | Station geographic region.
isynth = | I | Synthetic data flag: IRLDTA (Real data) ????? (Flags for various synthetic seismogram codes)
iztype = | I | Reference time equivalence: IUNKN (5): Unknown IB (9): Begin time IDAY (10): Midnight of reference GMT day IO (11): Event origin time IA (12): First arrival time ITn (13-22): User defined time pick n, n=0,9
ka = | K | First arrival time identification.
kcmpnm = | K | Component name.
kevnm = | K | Event name.
kf = | F | Fini or end of event time identification.
khole = | k | Hole identification if nuclear event.
kinst = | K | Generic name of recording instrument
knetwk = | K | Name of seismic network.
ko = | K | Event origin time identification.
kstnm = | K | Station name.
kt0 = | F | User defined time pick identification.
kt1 = | F | User defined time pick identification.
kt2 = | F | User defined time pick identification.
kt3 = | F | User defined time pick identification.
kt4 = | F | User defined time pick identification.
kt5 = | F | User defined time pick identification.
kt6 = | F | User defined time pick identification.
kt7 = | F | User defined time pick identification.
kt8 = | F | User defined time pick identification.
kt9 = | F | User defined time pick identification.
kuser0 = | K | User defined variable storage area 0.
kuser1 = | K | User defined variable storage area 1.
kuser2 = | K | User defined variable storage area 2.
lcalda = | L | TRUE if DIST AZ BAZ and GCARC are to be calculated from st event coordinates.
leven = | L | TRUE if data is evenly spaced.
lovrok = | L | TRUE if it is okay to overwrite this file on disk.
lpspol = | L | TRUE if station components have a positive polarity (left-hand rule).
mag = | F | Event magnitude.
nevid = | N | Event ID (CSS 3.0)
norid = | N | Origin ID (CSS 3.0)
npts = | N | Number of points per data component.
nvhdr = | N | Header version number. Current value is the integer 6. Older version data (NVHDR < 6) are automatically updated when read into sac.
nwfid = | N | Waveform ID (CSS 3.0)
nzhour = | N | GMT hour.
nzjday = | N | GMT julian day.
nzmin = | N | GMT minute.
nzmsec = | N | GMT millisecond.
nzsec = | N | GMT second.
nzyear = | N | GMT year corresponding to reference time in file.
o = | F | Event origin time (seconds relative to reference time.)
odelta = | F | Observed increment if different from nominal value.
scale = | F | Multiplying scale factor for dependent variable
stdp = | F | Station depth below surface (meters).
stel = | F | Station elevation (meters).
stla = | F | Station latitude (degrees, north positive)
stlo = | F | Station longitude (degrees, east positive).
t0 = | F | User defined time (seconds picks or markers relative to reference time).
t1 = | F | User defined time (seconds picks or markers relative to reference time).
t2 = | F | User defined time (seconds picks or markers relative to reference time).
t3 = | F | User defined time (seconds picks or markers relative to reference time).
t4 = | F | User defined time (seconds picks or markers relative to reference time).
t5 = | F | User defined time (seconds picks or markers relative to reference time).
t6 = | F | User defined time (seconds picks or markers relative to reference time).
t7 = | F | User defined time (seconds picks or markers relative to reference time).
t8 = | F | User defined time (seconds picks or markers relative to reference time).
t9 = | F | User defined time (seconds picks or markers relative to reference time).
user0 = | F | User defined variable storage area 0.
user1 = | F | User defined variable storage area 1.
user2 = | F | User defined variable storage area 2.
user3 = | F | User defined variable storage area 3.
user4 = | F | User defined variable storage area 4.
user5 = | F | User defined variable storage area 5.
user6 = | F | User defined variable storage area 6.
user7 = | F | User defined variable storage area 7.
user8 = | F | User defined variable storage area 8.
user9 = | F | User defined variable storage area 9.

### Thank you!

We would like to thank our contributors, whose efforts make this software what it is. These people have helped by writing code and documentation, and by testing. They have created and maintained this product, its associated libraries and applications, our build tools and our web sites.

#### Contributors

- Ackerley, Nick
- Allgeyer, Sebastien
- Ammon, Charles J.
- Antunes, Emanuel
- Arnarsson, Ólafur St.
- Bank, Markus
- Barsch, Robert
- Behr, Yannik
- Bernardi, Fabrizio
- Bernauer, Felix
- Bes de Berc, Maxime
- Beyreuther, Moritz
- Boltz, Shawn
- Bonaimé, Sébastien
- Carothers, Lloyd
- Chamberlain, Calum
- Chambers, Derrick
- Chen, Zhao
- Clark, Adam
- Danecek, Peter
- Egdorf, Sven
- Engels, Fabian
- Ermert, Laura
- Eulenfeld, Tom

- Fabbri, Tommaso
- Falco, Nicholas
- Fee, Jeremy
- Grellier, Clément
- Grunberg, Marc
- Hammer, Conny
- Heimann, Sebastian
- Heiniger, Lukas
- Hope, Gaute
- Igel, Heiner
- Inza, Adolfo
- Isken, Marius
- Ketchum, David
- Koymans, Mathijs
- Kremers, Simon
- Kress, Victor
- Krieger, Lars
- Krischer, Lion
- Kula, Damian
- Käufl, Paul
- Köhler, Andreas
- Lecocq, Thomas
- Leeman, John
- Legovini, Paride

- Lesage, Philippe
- Li, Yulin
- Lomax, Anthony
- Lopes, Rui L.
- MacCarthy, Jonathan
- Maggi, Alessia
- Martin, Henri
- Medlin, Andrew
- Megies, Tobias
- Meschede, Matthias
- Michelini, Alberto
- Miller, Nathaniel C.
- Morgenstern, Bernhard
- Nof, Ran Novitsky
- Panning, Mark P.
- Parker, Tom
- Pestourie, Romain
- Rapagnani, Giovanni
- Reyes, Celso
- Ringler, Adam
- Rothenhäusler, Nicolas
- Russo, Emiliano
- Sales de Andrade, Elliott

- Satriano, Claudio
- Saul, Joachim
- Scheingraber, Chris
- Schneider, Simon
- Sippl, Christian
- Snoke, Arthur
- Stange, Stefan
- Stähler, Simon C.
- Sullivan, Benjamin
- Tian, Dongdong
- Trabant, Chad
- Trani, Luca
- Uieda, Leonardo
- Walker, Andrew
- Walther, Marcus
- Wassermann, Joachim
- Williams, Mark C.
- Winkelman, Andrew
- Zaccarelli, Riccardo
- Zad, Seyed Kasra Hosseini
- Zhu, Lijun
- van Driel, Martin
- van Wijk, Kasper

#### Funds

ObsPy was partially funded by the

- German Science Foundation (DFG) via grant DFG IG 16/9-1
- German Ministry for Education and Research (BMBF), GEOTECHNOLOGIEN grant 03G0646H.
- NERA project (Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation) under the European Community's Seventh Framework Programme (FP7/2007-2013) grant agreement n° 262330
- Leibniz Institute for Applied Geophysics (LIAG)
- VERCE EU-FP7 project (no. 283543)