LOCSAT¶
Locator in SeisComP for computing source time and hypocenter coordinates from phase picks.
Description¶
LOCSAT is a locator in SeisComP for computing source time and hypocenter coordinates from phase picks considering:
Pick time,
Backazimuth,
Slowness.
The LOCSAT locator interface implements a wrapper for the LocSAT locator by Bratt and Nagy [16] (according to the README file shipped with the LocSAT distribution) referred to as LOCSAT in SeisComP.
Travel-time tables¶
SeisComP ships with two predefined travel time tables: tab and iasp91.
LOCSAT travel time tables are located under share/locsat/tables/
.
The default profile is iasp91.
Travel-time interface¶
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¶
Use “LOCSAT” as a value for the locator type or interface when configurable, e.g. by screloc or scolv.
Station corrections¶
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 [21]
station correction definitions.
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
with
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
Note
The fourth column (numReadings) is ignored and just provided for compatibility reasons with NonLinLoc.
Configuration¶
Note
LOCSAT.* Locator parameters: LOCSAT
-
LOCSAT.profiles
¶ Type: list:string
Defines a list of available LOCSAT travel-time tables. Default is
iasp91, tab
.
-
LOCSAT.depthInit
¶ Type: double
Unit: km
The initial depth estimate for LOCSAT. Default is
20.0
.
-
LOCSAT.usePickUncertainties
¶ Type: boolean
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
false
.
-
LOCSAT.defaultTimeError
¶ Type: double
Unit: s
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
1.0
.
-
LOCSAT.degreesOfFreedom
¶ Type: int
Number of degrees of freedom. Default is
9999
.
-
LOCSAT.confLevel
¶ Type: double
Confidence level between 0.5 and 1.0. Default is
0.9
.
-
LOCSAT.enableConfidenceEllipsoid
¶ Type: boolean
Compute the confidence ellipsoid from covariance matrix in 3D. Default is
false
.