Locator in SeisComP for computing source time and hypocenter coordinates from phase picks.
LOCSAT is a locator with a travel-time interface in SeisComP for computing source time and hypocenter coordinates from phase picks considering:
Pick time and pick uncertainty,
Backazimuth and backazimuth uncertainty,
Slowness and slowness uncertainty,
Phase-specfic travel-time tables.
The LOCSAT locator interface implements a wrapper for the LocSAT locator by Bratt and Nagy  (according to the README file shipped with the LocSAT distribution) referred to as LOCSAT in SeisComP. The LOCSAT travel-time interface provides travel time for specfic phases, epicentral distance, soure depth and station elevation.
LOCSAT provides the hypocenter parameters through the locator interface.
LOCSAT provides an interface for computing travel times based on coordinates and depth. The times are plotted on waveforms, e.g., blue marks in scolv picker window.
Use “LOCSAT” as a value for the travel-time interface when configurable, e.g., by FixedHypocenter.
SeisComP ships with two sets of predefined travel-time tables which are made available as the profiles tab and iasp91.
The default profile is iasp91.
LOCSAT travel time tables are located as plain ascii files under
The tables provide the travel times for particular seismic phases at
given depth and epicentral distance in one file per Earth model and seismic
phase. E.g. P-wave arrival times in the iasp91 model are found in
@DATADIR@/locsat/tables/iasp91.P. You may easily add your own tables
for any available Earth model and seismic phase by adopting existing ones in new
files which are added by configuration to
your SeisComP modules.
Only phases for which a travel-time table exists can be considered.
LOCSAT currently considers travel-time tables for phases which are hard-coded
seismic body waves: P, Pg, Pb, Pn, Rg, pP, sP, PKP, PP, PKPab, PKPbc, PKPdf, SKPdf, PcP, S, Sg, Sb, Sn, Lg, SKS, SS, ScS,
where P and S are the direct P and S phases, respectively, at all distances no matter the take-off angle at the source.
seismic surface waves: LQ, LR.
infrasound: Is, It, Iw.
The maximum number of distance and depth intervals per table file is currently 210 and 50, respectively.
Travel-time tables with larger numbers of distance or depth samples are reported along with command-line error output (stderr). The travel-time tables should therefore be tested, e.g., with scolv before unsupervised application.
Travel times at distance and depth samples exceeding the limits are ignored. This may lead to undesired behavior during location.
Phase picks observed outside the distance and depth ranges defined by travel-time tables may lead to undesired behavior during location.
The considered minimum depth is 0 km. Elevations and depths above datum are not natively considered. The effects of station elevation can be corrected for empirically.
LOCSAT does not natively support corrections of travel-time tables for station elevations. 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 emperic corrections of observed travel times.
The corrections are provided in seconds and subtracted (not added) from
the observation time to be compatible with the NonLinLoc 
station correction definitions.
Each LOCSAT profile (travel time table) can have one associated station
correction file. E.g. for adding station corrections to the iasp91 tables, the
$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.
Application and Setup¶
Custom travel-time tables¶
Generate your travel-time tables from a custom Earth model, depth and distance intervals. Use the same format as the defaults as the iasp91 tables. Tools such as allow the generation.
Add your custom travel-time tables along with station corrections to
Add your available custom LOCSAT travel-time tables in global configuration, e.g., to the list of tables of travel-time interfaces
ttt.LOCSAT.tables = iasp91, tab, custom
and to the list of locator profiles
LOCSAT.profiles = iasp91, tab, custom
and optionally to locators which make use of LOCSAT tables, e.g., FixedHypocenter.
Application with modules¶
Additional parameters of LOCSAT may be configured in global module configuration
The profiles for locating may be extended or limited by
Measurements of backazimuth and slowness may be deactivated by
LOCSAT.useSlownewss, respectively. Such measurements may be obtained from array processing or from feature extraction using scautopick.
You may also configure some SeisComP modules with LOCSAT and a profile.
scautoloc: Configure a profile for automatic locations,
screloc: Configure LOCSAT along with a profile for automatically relocating.
scolv: Configure LOCSAT along with a profile as defaults for interactive locations.
When using LOCSAT in scolv you may interactively some settings. The changes only apply during runtime.
LOCSAT.* Locator parameters: LOCSAT
Defines a list of available LOCSAT travel-time tables.
The initial depth estimate for LOCSAT.
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.
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.
Whether to forward pick backazimuth to LOCSAT or not. In an automatic mode backazimuth measurements might be inaccurrate and disabling their usage in LOCSAT can be controlled with this parameter.
Whether to forward pick horizontal slowness to LOCSAT or not. In an automatic mode slowness measurements might be inaccurrate and disabling their usage in LOCSAT can be controlled with this parameter.
Number of degrees of freedom.
Confidence level between 0.5 and 1.0.
Compute the confidence ellipsoid from covariance matrix in 3D.