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202 lines
4.6 KiB
ReStructuredText
202 lines
4.6 KiB
ReStructuredText
.. _global_locsat:
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######
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LOCSAT
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######
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Locator in SeisComP for computing source time and hypocenter
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coordinates from phase picks.
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Description
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===========
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LOCSAT is a locator in SeisComP for computing source time and hypocenter
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coordinates from phase picks considering:
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* Pick time,
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* Backazimuth,
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* Slowness.
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The LOCSAT locator interface implements a wrapper for the LocSAT locator
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by :cite:t:`bratt-1991` (according to the README file shipped with the
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LocSAT distribution) referred to as **LOCSAT** in |scname|.
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Travel-time tables
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==================
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|scname| ships with two predefined travel time tables: tab and iasp91.
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LOCSAT travel time tables are located under :file:`share/locsat/tables/`.
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The default profile is *iasp91*.
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Travel-time interface
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=====================
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LOCSAT provides an interface for computing travel times based on coordinates and depth.
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Use "LOCSAT" as a value for the travel-time interface when configurable, e.g. by
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:ref:`global_fixedhypocenter`.
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Configuration in |scname| modules
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=================================
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Use "LOCSAT" as a value for the locator type or interface when configurable, e.g. by
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:ref:`screloc` or :ref:`scolv`.
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Station corrections
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===================
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LOCSAT does not support station corrections natively. At least checking
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the code:
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.. code-block:: c
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sta_cor[i] = 0.0; /* FIX !!!!!!*/
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However the |scname| wrapper adds this feature. It allows to define a
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:file:`.stacor` file which defines corrections of observation times
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in seconds. A correction is **subtracted** (not added) from
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the observation time to be compatible with the NonLinLoc :cite:p:`nonlinloc`
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station correction definitions.
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Each LOCSAT profile (travel time table) can have an associated station
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correction file. To use station corrections for the iasp91 tables, the file
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:file:`$SEISCOMP_ROOT/share/locsat/tables/iasp91.stacor` needs to be created.
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A station correction table takes the form:
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.. code-block:: sh
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# LOCDELAY code phase numReadings delay
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LOCDELAY GE.MORC P 1 -0.1
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with
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- **code** (*string*) station code (after all alias evaluations)
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- **phase** (*string*) phase type (any of the available travel time tables)
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- **numReadings** (*integer*) number of residuals used to calculate mean residual/delay
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(not used by NLLoc, included for compatibility with the format of a summary,
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phase statistics file)
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- **delay** (*float*) delay in seconds, subtracted from observed time
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.. note::
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The fourth column (numReadings) is ignored and just provided for compatibility
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reasons with :ref:`NonLinLoc <global_nonlinloc>`.
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.. _global_locsat_configuration:
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Module Configuration
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====================
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.. note::
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**LOCSAT.\***
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*Locator parameters: LOCSAT*
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.. confval:: LOCSAT.profiles
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Default: ``iasp91, tab``
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Type: *list:string*
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Defines a list of available LOCSAT travel\-time tables.
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.. confval:: LOCSAT.depthInit
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Default: ``20.0``
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Type: *double*
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Unit: *km*
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The initial depth estimate for LOCSAT.
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.. confval:: LOCSAT.usePickUncertainties
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Default: ``false``
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Type: *boolean*
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Whether to use pick time untertainties for arrival deltim rather
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than a fixed time error. If true then the uncertainties are
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retrieved from each individual pick object. If they are not
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defined then the default pick time uncertainty will be used
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as fallback.
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.. confval:: LOCSAT.defaultTimeError
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Default: ``1.0``
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Type: *double*
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Unit: *s*
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The default pick time uncertainty assigned to LOCSAT's arrival deltim
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attribute if pick uncertainties are not going to be used or
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if they are absent. A time uncertainty of 0 s may result in
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errors of the SVD decomposition in LOCSAT.
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.. confval:: LOCSAT.usePickBackazimuth
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Default: ``true``
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Type: *boolean*
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Whether to forward pick backazimuth to LOCSAT or not. In an
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automatic mode backazimuth measurements might be inaccurrate
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and disabling their usage in LOCSAT can be controlled with
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this parameter.
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.. confval:: LOCSAT.usePickSlowness
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Default: ``true``
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Type: *boolean*
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Whether to forward pick horizontal slowness to LOCSAT or not.
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In an automatic mode slowness measurements might be
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inaccurrate and disabling their usage in LOCSAT can be
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controlled with this parameter.
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.. confval:: LOCSAT.degreesOfFreedom
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Default: ``9999``
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Type: *int*
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Number of degrees of freedom.
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.. confval:: LOCSAT.confLevel
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Default: ``0.9``
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Type: *double*
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Confidence level between 0.5 and 1.0.
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.. confval:: LOCSAT.enableConfidenceEllipsoid
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Default: ``false``
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Type: *boolean*
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Compute the confidence ellipsoid from covariance matrix in 3D.
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