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 [7] 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. [17].

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.