The two main programs in the automatic event detection and location processing chain, scautopick and scautoloc, only work together if the information needed by scautoloc can be supplied by scautopick. This document explains current implicit dependencies between these two utilities and is meant as a guide especially for those who plan to modify or replace one or both of these utilities by own developments.
Both scautopick and scautoloc are subject to ongoing developments. The explanation given below can therefore only be considered a hint, but not a standard.
The data scautoloc works with are primarily seismic phase picks. In addition, certain amplitudes are used as a kind of quality criterion for the pick, allowing picks with a higher absolute amplitude or signal-to-noise ratio to be given priority in the processing over weak low-quality picks.
Currently scautoloc only processes automatic, 1st-arrival P picks. Furthermore, in the current version of scautopick only P picks are produced anyway. It can therefore be safely assumed by scautoloc that any automatic pick is a P pick that either has a phaseHint attribute explicitly stating "P" ot the phaseHint attribute left empty. Automatic picks with a phaseHint other than "P" as well as any picks not tagged as automatic are currently ignored. It is thus highly recommended to always set the phaseHint attribute with the appropriate phase name. There is no restriction regarding the choice of the publicID of the pick.
Optionally scautoloc performance may be improved by processing certain amplitudes accompanying the picks. Two kinds of amplitudes may be used together
Neither amplitude is used for magnitude computation by scautoloc. The default amplitude types used by scautoloc are of type "mb" and "snr". These defaults can be overridden in scautoloc.cfg:
autoloc.amplTypeSNR = "snr" autoloc.amplTypeAbs = "mb"
If for instance an alternate picker implementation doesn't produce "mb"-type absolute amplitude but e.g. "xy", then autoloc.amplTypeAbs needs to be set to "xy" to have them recognized by scautoloc.
Currently there must be an absolute and a relative amplitude for every pick. However, this requirement will be relaxed in a future version. But currently scautoloc will always wait until both amplitude have arrived, which results in an overall processing delay, corresponding to the usually delayed availability of amplitudes with respect to the corresponding pick. The default absolute amplitude "mb", for instance, takes a hard-coded 30-seconds time interval to be computed. This length of data thus has to be waited for, plus a little extra because of the size of the MiniSEED records. An alternate picker implementation could produce a different absolute-amplitude type than "mb". That amplitude might be based on a different filter pass band and much shorter time window than the default "mb" amplitude, thus allowing a significantly improved processing speed. The choice of amplitude type and time window greatly depends on the network. For a regional or even global network the 30-seconds processing delay won't play a role, and we need the mb amplitude anyway. Here the delay of solutions produced by scautoloc is mostly controlled by the seismic traveltimes. Not so in case of a local or small-regional network, where the mb-type amplitude is of limited value and where a meaningful absolute amplitude might well be produced with just a second of data and at higher frequencies. Currently this isn't possible with scautopick but this issue will be addressed in a future version.