
Date July 23 2002

The following is a description of SAC header values that are
used by programs in the computer program sin seismology suite.
Although particular header value may have more than one meaning, but
header values are chosen to be consistent with the particular
use of a SAC file.

Header  Variable        Definition      Programs        Language        

USER1   permin  Minimum usable period   sacmat96        F77
                                        sacmft96        F77
                                        sacpom96        F77
                                        sacevalr        F77
                                        sacfilt         F77
KUSER1  PER_MIN identifier flag


USER2   permax  Maximum usable period   sacmat96        F77
                                        sacmft96        F77
                                        sacpom96        F77
                                        sacevalr        F77
                                        sacfilt         F77
KUSER2  PER_MAX identifier flag

[ The purpose of these flags is to identify the usable period range in
  a data set. For example, phase-match filtering of a surface wave
  is limited to the range of periods in the group velocity data set. 
  Further processing of a phase match filtered trace, should not
  be permitted to use periods outside this range since the signal lacks
  these spectral components.  sacmft96 and sacmat96 use these flags.

  The programs sacfilt and sacevalr permit deconvolving of instrument
  response from a signal. Deconvolution is made stable by applying
  a water level deconvolution  to yield a stable output signal. 
  The permin and permax are set to indicate the range of periods
  within the bounds of the high and low pass filters applied as part
  of the water level deconvolution ]

KUSER1  FD_DECON                        rftndr96        F77
                                        hrftn96         F77
                                        trftn96         F77
                                        sacdecon        F77

KUSER1  IT_DECON                        saciterd        C

[ This is an informational flag that indicates the type of
  deconvolution performed, FD to frequency domain or TD for time domain.
  The receiver functions arising from hrftn96 trfth96 and rftndr96
  are are acceptable since these are based on synthetics and the
  deconvolution process is stable.

  sacdecon permits a receiver function to be computed by a water level
  deconvolution. We prefer the iterative time domain deconvolution program 
  saciterd for stability ]

USER0   gauss   Gauss filter parameter  jntpre96        F77
                                        rftndr96        F77
                                        rftnpr96        F77
                                        hrftn96         F77
                                        trftn96         F77
                                        saciterd        F77
KUSER0  Rftn                            rftndr96        F77
                                        saciterd        F77
                                        hrftn96         F77
                                        trftn96         F77
        Decon                           sacdecon        F77

[ These flags are used to denote the resulting time series, e.g.,
  either it is a receiver function or it is a deconvolution of
  two time series.

  The parameter gauss is the Gaussian Alpha filter parameter defined
  by Ammon et al (19XX) to control high frequency noise in a 
  deconvolution ]

USER5   fit     Goodness of fit         saciterd        F77
KUSER5  FIT                             saciterd        F77

[ This is a quantitative measure of the goodness of fit of a 
  receiver function. It is defined as 100 x SUM (obs - pred)/SUM obs
  or such.  A high value reflects the quality of the original signals
  used to obtain the receiver function ]

USER5   100.0   Goodness of fit         rftndr96        F77
                                        hrftn96         F77
                                        trftn96         F77

[ By definition (and hopefully good programming), the goodness of fit
  for synthetic RFTN's is perfect ]

USER4   rayp    Ray parameter (sec/km)  hrftn96         F77
                                        trftn96         F77
                                        rftnpr96        F77
                                        rftndr96        F77
                                        saciterd        F77
[ The computation of receiver functions requires a ray parameter.
  At present the user must remember which phase is associated with the
  value, either P or S. The program saciterd does not use this value,
  but instead places it in the SAC header if given ont he saciterd
  command line. ]

KEVNM   Rftn                            rftndr96        F77
                                        hrftn96         F77
                                        trftn96         F77
KCMPNM  Rftn                            rftndr96        F77
                                        hrftn96        	F77
                                        trftn96        	F77
[ These are identifiers set to identify a trace as a receiver function.
  NOTE WE SHOULD PROBABLY TRY TO BE MORE PRECISE AND DENOTE
  P or S or Radial or Transverse RFTN's ]

KA      P                               f96tosac
KT0     SV                              f96tosac
KT1     SH                              f96tosac

A       ptime                           f96tosac
T0      svtime                          f96tosac
T1      shtime                          f96tosac

[ The program f96tosac converts the ASCII file96 timeseries to SAC
  binary or alpha files. The surface wave and wavenumber integration programs
  compute the expected first arrival of P, SV and SH signals. The SV and SH
  first arrivals are different in TI media. 

  This distinction becomes odd when the Z R and T traces are rotated to
  form Z N E traces when invoking fmech96 (fmech96 reads Green's functions
  and writes a 3-component trace).  At present these are written to the header.

  LOGICALLY I SHOULD BE MORE CAREFUL, e.g., for R component out tsv in T0
  and for T componet put tsh in T0, for N or E put earlier of tsv or tsh in T0
  so that an S is always in  T0 ]
