• Antelope Release 5.5 Mac OS X 10.8.5 2015-04-21

 

NAME

eqerror - collection of functions for computing earthquake location errors

SYNOPSIS

#include "location.h"
void predicted_errors(Hypocenter h, Tbl *attbl, Tbl *utbl,
	Location_options o, double **C, float *emodel)
int project_covariance(double **C, int model, double *conf, double rms,
	int dgf, double *smajax, double *sminax, double *strike,
	double *sdepth, double *stime)

SUPPORT


Contributed code: NO BRTT support.
THIS PIECE OF SOFTWARE WAS CONTRIBUTED BY THE ANTELOPE USER COMMUNITY. BRTT DISCLAIMS ALL OWNERSHIP, LIABILITY, AND SUPPORT FOR THIS PIECE OF SOFTWARE.

FOR HELP WITH THIS PIECE OF SOFTWARE, PLEASE CONTACT THE CONTRIBUTING AUTHOR.

DESCRIPTION

This pair of routines is used to compute location error estimates in the genloc location package. The predicted_errors function computes the fundamental components used to estimate a location error estimate and project_covariance is a more specialized function used to convert the raw covariance returned by predicted_errors to error ellipse parameters needed for saving in a css3.0 database.

predicted_errors arguments:

project_covariance arguments:

smajax, sminax, and strike are outputs that define the major axis, minor axis, and strike angle (azimuth in degrees from north) of the major axis for the epicentral error ellipse.

sdepth and stime are depth and origin time error estimates as defined in css3.0's origerr table. Note that project_covariance uses an algorithm that uses the largest projection of each of the four axes of the 4-d error ellipsoid onto the respective component axis.

RETURN VALUES

project_covariance normally returns 0. It returns -1 if the eigenvalue decomposition routine used gets garbage input and a positive number if the eigenvalue decomposition had convergence errors.

SEE ALSO

genloc_intro(3), ggnloc(3)

BUGS AND CAVEATS

Error ellipses are most sensible for appraising measurement errors and it is the author's prejudice that the F_DIST generated error ellipses are misleading. emodel error bounds have problems also in that they depend upon a scale factor (defined in phase definitions for genloc) to mean anything. This scale factor, in practice, can be difficult to define accurately.

AUTHOR

Gary L. Pavlis
Antelope User Group Contributed Software
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