scevent

Associates Origins to Events or forms new Events if no suitable match is found. Selects preferred magnitude.

As a consequence of a real-time system the SeisComP3 system creates several origins (results of localization processes) for one earthquake because as time goes by more seismic phases are available. scevent receives these origins and associates the origins to events. It is also possible to import Origins from other agencies.

Origin Matching

Scevent associates Origins to Events by searching for the best match of the new (incoming) Origin to other Origins for existing Events. If a match is not found a new Event can be formed. The new Origin is matched to existing Origin by comparing location difference (horizontal only), Origin time difference, and matching Picks. The first best match is preferred where the options for an Origin match are (lowest to highest);

(1) Location and Time (lowest)

The difference in horizontal location is less than eventAssociation.maximumDistance (degrees) and the difference in Origin times is less than eventAssociation.maximumTimeSpan

(2) Picks

the two Origins have more than eventAssociation.minimumMatchingArrivals matching Picks. Note (check this with Jan) it appears that Pick equality is based only on publicID. This effectively means that for Picks to be equal they will need to be created by the same picker configuration.

(3) Picks and Location and Time (highest)

this is the best match, both of the Location-and-Time and Picks criteria above are satisfied.

Notes: for efficiency Events in the cache are scanned first and if no matches are found then the database is scanned for the time window eventAssociation.eventTimeBefore eventAssociation.eventTimeAfter around the incoming Origin time.

The order of objects in the cache will affect the first best match - is the time or insertion ordered?

Possible Improvements (Geoff and Rich to discuss with Jan) The location and time comparison could be improved by finding the Origin with the minium delta time and difference. The Pick comparison could be improved by fuzzy matching on Pick time, Name, and Channel.

No Origin Match

If no Event with an Origin that matches the incoming Origin is found then a new Event is formed and the Origin is associated to that Event. The following criteria are applied to allow the creation of the new Event:

The Agency for the Origin is not black listed (processing.blacklist.agencies).

and

If the Origin is an Automatic then it has more than eventAssociation.minimumDefiningPhases Picks.


Figure 5-1: Association of an origin by matching_picks

Preferred Origin

As already mentioned, one earthquake can be represented by several origins. So, one origin has to be chosen among the associated origins representing the location and time best. This is done by the following rules:

  1. The latest manual or confirmed origin has the highest priority and is always preferred
  2. Manual or confirmed origins have always a higher priority than automatic origins
  3. In case the actual preferred origin is automatic, the incoming automatic origin will be preferred, if it contains more arrivals/phases and has a network magnitude being a possible preferred magnitude

Preferred Magnitude

The third task of scevent is to choose the preferred magnitude. For this purpose the following rules are used:

  1. Network magnitudes are only valid if more than a defined number of station magnitudes exist (default=3). Mw(mB) is a strong motion magnitude resulting in special criteria: Mw(mB) is valid if equal or more than a defined amount of station magnitudes exist (default=8).
  2. The priority of magnitudes is Mw(mB), MLv, mb (from high to low). For Mw(mB) additional priority criteria are defined.
    • If more than a defined number of station magnitudes exist for Mw(mB) (default = 30), Mw(mB) will always be preferred
    • If less than the defined number of station magnitudes exist for Mw(mB) (default = 30), Mw(mB) will be preferred when
      1. The sum of all stations magnitudes for Mw(mB) and for mb divided by 2 is more than a defined value (default = 6)
      2. If the number of station magnitudes for Mw(mB) is greater or equal than half of the station magnitude count for mb

Options

scevent supports configuration files (scevent.cfg).

Configuration

eventAssociation.minimumMagnitudes = <int>
Minimum number of station magnitudes referenced to a network magnitude to become a preferred magnitude. Default is 4.
eventAssociation.minimumMatchingArrivals = <int>
Minimum number of matching picks between two origins to be associated to the same event. Default is 3.
eventAssociation.minimumDefiningPhases = <int>
Minimum number of Picks for an Origin that is automatic and cannot be associated with an Event to be allowed to form an new Event. Default is 10.
eventAssociation.eventTimeBefore = <int>
Time range (seconds) before the origin time of an incoming origin to search for matching events. Default is 1800 seconds.
eventAssociation.eventTimeAfter = <int>
Time range (seconds) after the origin time of an incoming origin to search for matching events. Default is 1800 seconds.
eventAssociation.maximumTimeSpan = <int>
Allowed origin time difference between an incoming origin compared with preferred origins to get associated. Default is 60 seconds.
eventAssociation.maximumDistance = <double>
Allowed location difference between an incoming origin compared with preferred origins to get associated. Default is 5°.
eventAssociation.minMwCount = <int>
Minimum number of station magnitudes required for Mw(mB) to get valid. Default is 8.
eventAssociation.mbOverMwCount = <int>
Minimum number of station magnitudes which ensures that Mw(mB) will be preferred and not mb. Default is 30, see magnitude rule 2.2
eventAssociation.mbOverMwValue = <double>
Average between mb and Mw(mB) which must be exceeded to become Mw(mB) preferred. Default is 6, see magnitude rule 2.2.1
eventIDPrefix = <string>
Prefix for all Event IDs
eventAssociation.enableFallbackMagnitude = <bool>
If true, one magnitude will be preferred even if magnitude criteria are not fullfilled
eventAssociation.magTypes = [mBc, Mw(mB), Mwp, ML, MLh, MLv, mb]
Magnitude type priority list for becoming a preferred magnitude for an event. See below for examples.
eventAssociation.agencies = <list>
The agencyID priority list. When the eventtool comes to the point to select a preferred origin it orders all origins by its agency priority and selects then the best one among the highest priority agency. It also defines the agency priority for custom priority checks (eventAssociation.priorities)

<New options in SC3 Potsdam>

eventAssociation.authors = <list>
The author priority list. When the eventtool comes to the point to select a preferred origin it orders all origins by its author priority and selects then the best one among the highest priority author. It also defines the author priority for custom priority checks (eventAssociation.priorities).

eventAssociation.priorities = <list>:

The general priority list to decide if an origin becomes preferred. This feature is still experimental and not used unless this parameter is activated. The default 

    eventAssociation.priorities = AGENCY, STATUS, PHASES_AUTOMATIC, TIME_AUTOMATIC

replicates the old hard wired behaviour. There are several criteria that are processed from first to last. Whenever a criterion evaluates to true the current origin becomes preferred. The following criteria are available:

AGENCY check based on agency priorities
AUTHOR check based on author priorities
STATUS manual origins rule out automatic ones
METHOD check based on the method priorities
PHASES higher phase count = higher priority
PHASES_AUTOMATIC only checks phase priorities for incoming automatic origins
RMS lower rms = higher priority
RMS_AUTMATIC only check RMS on incoming automatic origins
TIME more recent origins (creationTime) have higher priorities
TIME_AUTOMATIC only checks creationTime priority on incoming automatic origins

Example of scevent.cfg: 

eventAssociation.minimumMagnitudes = 4
eventAssociation.minimumDefiningPhases = 10
eventAssociation.eventTimeBefore = 1800
eventAssociation.eventTimeAfter = 1800
eventAssociation.minimumMatchingArrivals = 3
eventAssociation.maximumTimeGap = 60
eventAssociation.maximumDistance = 5
eventAssociation.minMwCount = 8
eventAssociation.mbOverMwCount = 30
eventAssociation.mbOverMwValue = 6
eventAssociation.magTypes = mBc, Mw(mB), ML, MLh, MLv, mb
eventIDPrefix = "gfz"

Preferred Magnitude

Used to define the priority order for a magnitude to become preferred e.g., if set to 

eventAssociation.magTypes = Mw(mB), MLv, MLh and an Mw(mB)

and an Mw(mB) magnitude that passes the other criteria for being preferred (c.f., eventAssociation.minimumMagnitudes etc) then it will be preferred. If there is no Mw(mB) available (or it does not satisfy the other preferred magnitude criteria) but there is an MLv magnitude available that does satisfy the criteria then the MLv magnitude will be set preferred and so on through the list.

To add the summary magnitude to list make sure it is enabled and add the name set in summaryMagnitude.type to the list or make it the only magnitude on the list e.g. 

eventAssociation.magTypes = M

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