LOCSAT locator in SeisComP for computing source time and hypocenter coordinates from phase picks.
The LOCSAT locator interface implements a wrapper for the LocSAT locator by S.R. Bratt and W. Nagy 1 (according to the README file shipped with the LocSAT distribution) referred to as LOCSAT in SeisComP.
SeisComP ships with two predefined travel time tables: tab and iasp91.
LOCSAT travel time tables are located under
The default profile is iasp91.
LOCSAT provides an interface for computing travel times based on coordinates and depth.
Use “LOCSAT” as a value for the travel-time interface when configurable, e.g. by FixedHypocenter.
Configuration in SeisComP modules¶
LOCSAT does not support station corrections natively. At least checking the code:
sta_cor[i] = 0.0; /* FIX !!!!!!*/
However the SeisComP wrapper adds this feature. It allows to define a
.stacor file which defines corrections of observation times
in seconds. A correction is subtracted (not added) from
the observation time to be compatible with the NonLinLoc station correction
Each LOCSAT profile (travel time table) can have an associated station
correction file. To use station corrections for the iasp91 tables, the file
$SEISCOMP_ROOT/share/locsat/tables/iasp91.stacor needs to be created.
A station correction table takes the form:
# LOCDELAY code phase numReadings delay LOCDELAY GE.MORC P 1 -0.1
code (string) station code (after all alias evaluations)
phase (string) phase type (any of the available travel time tables)
numReadings (integer) number of residuals used to calculate mean residual/delay (not used by NLLoc, included for compatibility with the format of a summary, phase statistics file)
delay (float) delay in seconds, subtracted from observed time
The fourth column (numReadings) is ignored and just provided for compatibility reasons with NonLinLoc.
S.R. Bratt and W. Nagy 1991). The LocSAT Program, Science Applications International Corporation (SAIC), San Diego.
NonLinLoc station corrections: http://alomax.free.fr/nlloc/soft3.03/control.html#_NLLoc_locdelay_
LOCSAT.* Locator parameters: LOCSAT
Defines a list of available LOCSAT travel-time tables. Default is
Compute the confidence ellipsoid. Default is
The initial depth estimate for LOCSAT. Default is
The default pick time uncertainty assigned to LOCSAT’s arrival deltim attribute if pick uncertainties are not going to be used or if they are absent. A time uncertainty of 0 s may result in errors of the SVD decomposition in LOCSAT. Default is
Whether to use pick time untertainties for arrival deltim rather than a fixed time error. If true then the uncertainties are retrieved from each individual pick object. If they are not defined then the default pick time uncertainty will be used as fallback. Default is
Number of degrees of freedom. Default is
Confidence level between 0.5 and 1. Default is