.. _catalyst-sec-terms:

Glossary
========

Terms as they are used in |appname| and in this documentation.

Active origin
   The origin selected in the origin table. The Active origin panel and the
   diagnostic plots always show it; most buttons work on it, or on all
   selected origins.

Aggregation
   Combining the picks of the same phase at one station that were made by
   several pickers or several times into one group, kept as is or replaced by
   a virtual pick. See :ref:`catalyst-sec-aggregation`.

Analyst rules
   The decision rules an analyst follows when reading the Travel-time plot:
   which picks to associate, which to drop, when to relocate. Smart-locate
   applies them automatically. See :ref:`catalyst-sec-analysis-rules`.

Array pick
   A pick of an array or beam that carries a back-azimuth and a slowness, as
   produced for infrasound and seismic arrays.

Back-azimuth
   Direction from the station to the source, clockwise from north. Measured
   back-azimuths are compared with the predicted ones on the Baz residual
   plot and are used by the *Azimuth* locator.

Candidate
   The result of Relocate or Smart-locate for a single origin, shown in the
   diagnostic plots next to the current solution. **Accept origin** replaces
   the origin with it. See :ref:`catalyst-sec-refine`.

Celerity
   Horizontal distance divided by travel time of an infrasound arrival
   (Is phase), typically 0.27 to 0.34 km/s. It is shown as the celerity band
   on the Move-out plot.

Clustering
   Grouping of the origins shown on the map by their hypocentres (eps,
   min size, depth weight). The clusters colour the 3D view and the cluster
   legend.

Double difference (DD)
   Relocation from the differences of travel-time residuals between nearby
   events, against a reference catalogue or relative to one another
   :cite:p:`waldhauser-2000`. See :ref:`catalyst-sec-refine-dd`.

Is phase
   An infrasound arrival. Is picks are drawn as triangles in all plots.

Mismatch
   Weighted fraction of the nearby stations that were available but not used
   by an origin. A high value points to a mislocation. See
   :ref:`catalyst-sec-qc-metrics`.

Move-out
   Reduced travel time (travel time minus distance divided by a velocity)
   against distance. Picks of one event line up when the velocity is right.

Nucleation
   Forming candidate events from picks that are not yet associated, with
   DBSCAN, back projection, GaMMA-lite or a grid search following the
   scautoloc approach. See :ref:`catalyst-sec-nucleation`.

Pick state
   Whether a pick is used by the active origin, associated but not used,
   pending to be added or removed, or not associated. It sets the colours of
   the pick marker, see :ref:`catalyst-sec-vis-active`.

Processing profile
   A named set of GUI settings for a network or region, stored in a
   ``.profile`` file and selected in the toolbar. See
   :ref:`catalyst-sec-profiles`.

QC rule set
   A named set of conditions on the quality metrics, used to select, star,
   confirm or reject origins. See :ref:`catalyst-sec-qc-rules`.

QC zone
   A polygon loaded from GeoJSON that assigns origins to a region, so that
   rules can depend on where an event is. See :ref:`catalyst-sec-qc-zones`.

Smart-locate
   Association, relocation and recovery of an origin following the analyst
   rules, in several steps from clean-up to the minimum number of phases.
   See :ref:`catalyst-sec-analysis-rules`.

Swarm recovery
   Finding events that nucleation missed by matching unused picks against
   the arrival patterns of well-located events (template match, swarm
   consensus). See :ref:`catalyst-sec-refine-swarm`.

Trace velocity
   Apparent horizontal velocity of a wave across an array, the inverse of
   the slowness. For infrasound it is used to filter the array picks, see
   :ref:`catalyst-sec-aggregation`.

Virtual pick
   A pick created by aggregation that stands for a group of picks. It exists
   only in |appname| and is never sent; its methodID starts with
   ``aggregated``.

Wadati diagram
   S−P time against P time after the first P for stations with both phases.
   The slope plus one is the Vp/Vs ratio. See :ref:`catalyst-sec-vis-wadati`.