Glossary

Terms as they are used in catalyst 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 Pick aggregation and filtering.

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 Analyst rules and Smart-locate.

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 Refining origins.

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 [5]. See DD tab: double-difference relocation.

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 Quality 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 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 Active origin panel.

Processing profile

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

QC rule set

A named set of conditions on the quality metrics, used to select, star, confirm or reject origins. See Conditions and 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 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 Analyst rules and Smart-locate.

Swarm recovery

Finding events that nucleation missed by matching unused picks against the arrival patterns of well-located events (template match, swarm consensus). See Swarm tab: recovering further events.

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 Pick aggregation and filtering.

Virtual pick

A pick created by aggregation that stands for a group of picks. It exists only in catalyst 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 Wadati.