Travel-Time Tables

Predictions of phase arrival times are required for backprojection and for indicating theoretical arrival times. They are either provided as

  • Travel-time tables for LOCSAT [1] are located in @DATADIR@/locsat/tables. One file per considered model and phase type must exist in that directory named as [model].[phase].

  • Velocity models for libtau in @DATADIR@/ttt. The provided models are ak135 and iasp91. The model files should not be changed.

General parameters can be adjusted by global module configuration.

  • Example for LOCSAT and libtau adding the model iasp91_scanloc which ships the scanloc [5] package:

    ttt.LOCSAT.tables = iasp91,iasp91_scanloc
    ttt.libtau.tables = iasp91,ak135
    

For viewing the phases in scolv, they must be added to the configuration in scolv.cfg, e.g.:

picker.showPhases = P,Pn,Pg,pP,sP,S,Sg,Iw

Seismic phases

Existing seismic travel-times for or velocity models for libtau can be used. New models and files for phases can be added for LOCSAT.

Infrasound phases

LAMBDA ships with travel-time tables predicting the arrival of infrasound phases for LOCSAT [1]. The table files are located in @DATADIR@/locsat/tables. The phase names are derived from Brown et al. [10].

Phase name

Table file

Meaning

ILm

Lambda wave arrival

Is

iasp91.Is

Stratospheric arrival

Isx

Stratospheric coda phase arrival

It

iasp91.It

Thermospheric arrival

Itx

Thermospheric coda phase arrival

Iw

iasp91.Iw

Tropospheric level wind generated arrival

Iwx

Tropospheric level wind generated coda phase arrival

N

Tropospheric level wind generated arrival

These travel-time tables are only rough estimates of the arrival times of sound waves at the given distances and source depth / elevation. Currently, we recommend to use only the backazimuth from infrasound detection for event location.