.. _catalyst-sec-aggregation: Pick aggregation and filtering ============================== Automatic pickers often produce several picks of the same phase at one station within a short time, for example when several pickers run in parallel or a picker triggers repeatedly on one arrival. Such duplicates distort nucleation, because one arrival counts several times, and they confuse the locator, which sees two different times for the same station and phase. Aggregation reduces each group of duplicate picks to one pick. Pick filters hide picks that should not take part in nucleation. .. _catalyst-sec-aggregation-clusters: How picks are grouped --------------------- Picks are grouped per station and phase. Within one station and phase, the picks are sorted by time, and a gap larger than **Dup. win** starts a new group. Each group becomes one pick. With the profile key ``aggAcrossPhases = true``, picks of different phases at one station are grouped together. Press **Aggregate** in **Pick processing → Aggregation** to run it. With ``dbAggregate = true`` in the profile, or **aggregate** ticked in the database bar, the picks are aggregated automatically after every load. Modes ----- Generate virtual pick ^^^^^^^^^^^^^^^^^^^^^ One new *virtual* pick is created per group, and the original picks are kept and tagged. The virtual pick gets: * a time chosen by **Time**: the first pick, the 5th percentile, the median, the 95th percentile or the last pick of the group. The percentiles are robust against a single outlier. * the measurements ticked under **Carry**: * **Backazimuth:** the circular mean over the group, * **Slowness:** the mean horizontal slowness, * **Onset:** the majority onset (impulsive or emergent), * **Polarity:** the majority polarity. Virtual picks have a methodID starting with ``aggregated``, and the pick table can show them alone or hide them (see :ref:`catalyst-sec-pickfilters`). Virtual picks exist only in |appname|. When origins are sent to the messaging system, arrivals that refer to virtual picks are removed first, because the rest of |scname| does not know these picks. With **Consider virtual picks** in the Relocate group, the locator also sees the source picks of each virtual pick, as arrivals with weight 0: they are shown but do not pull the solution. Keep preferred pick ^^^^^^^^^^^^^^^^^^^ One real pick per group is kept, and the others are **deleted** from the working set. This cannot be undone in |appname|; reload the data to get the picks back. The pick to keep is chosen by the priority list under **Advanced parameters**. The rules are compared from top to bottom, and a tie falls through to the next rule: .. csv-table:: :header: "Rule", "Preference" :widths: 30, 70 "Manual", "Manual picks before automatic ones." "Status", "The more vetted evaluation status." "Time uncertainty", "The smaller time uncertainty." "Time", "The earliest or the latest pick." "Author", "A named author, for example a preferred picker." "Method", "A named methodID." The list is saved in the profile as ``pickPrefRules``. .. _catalyst-sec-pickfilters: Pick filters ------------ The pick filters are opened with the filter button of the **Picks** panel. Hidden picks are not used for nucleation, but they can still be associated to origins. .. csv-table:: :header: "Filter", "Description" :widths: 30, 70 "Show associated / unassociated", "Show the picks that belong to an origin, the picks that belong to none, or both. These are view filters only: nucleation always works on the unassociated picks." "Only the selected origin", "Show only the picks of the origin selected in the origin table." "Network, Station, Phase", "Comma-separated codes. Empty = any." "Station lat / lon", "Show only picks from stations inside the range." "Aggregation", "*All picks*, *Aggregated only*, *Originals only*, *Not isolated* or *Isolated only*." "Time", "Show only picks within a time window." "Slow/Baz", "The sectors selected in the Slow/Baz chart (see :ref:`catalyst-sec-vis-slowbaz`), including the Is band, shown here as a summary that can be switched off." Histogram bins ^^^^^^^^^^^^^^ Clicking a bar of the pick histogram shows only the picks of that time bin. **Ctrl+click** adds or removes single bins, and **Shift+click** selects the range of bins from the last clicked one, so several separate time ranges can be selected. The selected bars are highlighted. Isolated picks ^^^^^^^^^^^^^^ A pick is *isolated* when too few other stations picked at about the same time. Isolated picks are usually noise. The limits are profile settings: .. csv-table:: :header: "Profile key", "Default", "Meaning" :widths: 30, 10, 60 "``pickIsoMinStations``", "2", "Minimum number of other stations picking within the window." "``pickIsoWindow``", "10", "Half-width of the time window [s]." "``pickIsoOverdetectingOnly``", "", "``true``: only picks of :ref:`over-detecting stations ` can count as isolated." Infrasound trace velocity ^^^^^^^^^^^^^^^^^^^^^^^^^ An infrasound array pick with a slowness has a trace velocity of 111.19 km/deg divided by the slowness. A signal from the atmosphere crosses the array at about 0.30–0.45 km/s. Slower detections are usually wind noise; faster ones are seismic or coupled signals. This range is the **Is band** of the Slow/Baz chart (see :ref:`catalyst-sec-vis-slowbaz`): select the band to keep only atmospheric infrasound, and right-click it to change the limits. They follow the European Infrasound Bulletin and are saved in the profile as ``pickIsTraceVelMin`` and ``pickIsTraceVelMax``. Picks without a slowness and picks of other phases are not affected.