SUMMARY

Computes the broadband frequency-wavenumber (FK) spectral estimate, using all files in SAC memory.

SYNTAX

BBFK {FILTER} {NORMALIZE} {EPS v} {MLM | PDS}
   {EXP n} {WAVENUMBER v} {SIZE m n} {LEVELS n}
   {DB} {TITLE text} {WRITE {ON | OFF} fname} {SSQ n}
   {PRINT {pname} }

INPUT

FILTER: Apply the bandpass filter designed in the most recent FILTERDESIGN command.

NORMALIZE: Normalizes the covariance matrix with the Capo method. A good idea if the signals vary much in amplitude among channels.

EPS v: Regularization quantity for covariance matrix. Diagonal matrix entries are multiplied by (1.0 + EPS).

MLM: Use maximum likelihood method for high-resolution estimate.

PDS: Take power density spectra without maximum likelihood method.

EXP n: Power to which the wavenumber spectrum will be raised.

WAVENUMBER v: Number of waves from which to sample spectral estimates.

SIZE m n: Size of contour plot in polar mode: m is an even num of plot samples in the azimuth direction; n is an even num of plot samples in the wavenumber direction (m*n is limited to 40,000).

LEVELS n: Number of contour intervals.

DB: Log scaling of plot in decibels.

TITLE text:

Title used in plot.

WRITE {ON | OFF} fname:

Whether to compute & write contour data in square mode to disk (as a type xyz SAC file). fname is file or path name (may be an absolute or relative). If no filename has been specified, the default is "BBFK". ON will reactivate fname most recently used. OFF turns writing off.

SSQ n: Size of the square (number of samples taken along each margin of the square). Maximum allowed is 200.

PRINT {pname}: Prints the resulting plot to the printer named in pname, or to the default printer if pname is not used. (This makes use of the SGF capability.)

FILTER:	Apply the bandpass filter designed in the most recent FILTERDESIGN command.
NORMALIZE:	Normalizes the covariance matrix with the Capo method. A good idea if the signals vary much in amplitude among channels.
EPS v:	Regularization quantity for covariance matrix. Diagonal matrix entries are multiplied by (1.0 + EPS).
MLM:	Use maximum likelihood method for high-resolution estimate.
PDS:	Take power density spectra without maximum likelihood method.
EXP n:	Power to which the wavenumber spectrum will be raised.
WAVENUMBER v:	Number of waves from which to sample spectral estimates.
SIZE m n:	Size of contour plot in polar mode: m is an even num of plot samples in the azimuth direction; n is an even num of plot samples in the wavenumber direction (m*n is limited to 40,000).
LEVELS n:	Number of contour intervals.
DB:	Log scaling of plot in decibels.
TITLE text:
	Title used in plot.
WRITE {ON \| OFF} fname:
	Whether to compute & write contour data in square mode to disk (as a type xyz SAC file). fname is file or path name (may be an absolute or relative). If no filename has been specified, the default is "BBFK". ON will reactivate fname most recently used. OFF turns writing off.
SSQ n:	Size of the square (number of samples taken along each margin of the square). Maximum allowed is 200.
PRINT {pname}:	Prints the resulting plot to the printer named in pname, or to the default printer if pname is not used. (This makes use of the SGF capability.)

DEFAULT VALUES

BBFK EPS .01 PDS EXP 1 WVENUMBER 1.0 SIZE 90 32 LEVELS 11 WRITE OFF SSQ 100
      (SSQ matters only if WRITE has been positively specified).

DESCRIPTION

The BBFK command allows the user to compute broadband frequency wavenumber spectra. It is based on the work of NAWAB et al., 1985 and many other references in the seismic and engineering literature.

HEADER DATA

The following logic is used to determine how to choose or calculate station/event offsets:

Case 1: If a reference station is set in KUSER1 and is the same for all files, and USER7 and USER8 are set for all files, USER7 and USER8 are used as offsets.

Case 2: If station latitude (STLA) and station longitude (STLO) are set for all files, offsets are calculated using these, using the first file as the reference station.

Case 3: If USER7 and USER8 are set for all files, they are used as offsets.

Case 4: If event latitude (EVLA) and event longitude (EVLO) are set

for all files then these are used to calculate offsets, using the first station as the reference station.

OUTPUT

The polar output is plotted immediately (not retained), the square output if requested is written out to disk. The FK peak, back azimuth and wavenumber are written to blackboard variables BBFK_AMP, BBFK_BAZIM and BBFK_WVNBR respectively.

ERROR MESSAGES

Size m or n not an even number. Offsets X,Y,Z not set in USER7,8,9 of headers. Coefficients produced by FILTERDESIGN not found, or filter type used was not "BP".

LIMITATIONS

The maximum number of stations allowed is 100. The maximum size of polar contour plot is m x n = 40,000. The maximum size of square contour output is i = 200.

SEE COMMANDS

MAP: for plotting stations in an array, according to X,Y offsets stored in SAC header variables USER7 & USER8.

REFERENCES

Nawab, SH, FU Dowla, and RT Lacoss, Direction determination of wideband signals, IEEE Trans. Acous. Speech Sig. Proc., 33: (5), 1114-1122, 1985

LATEST REVISION

July 22, 1991 (Version 10.6c)