TTIMES(1)

NAME
ttimes - travel time table access using tau-splines

SYNOPSIS
ttimes [ -debug ] [ -units [ km | deg ]] [ -verbose | -terse ] [ -takeoff ] [ -model name ]

DESCRIPTION
ttimes is a simple user interface to access the travel times for a wide variety of seismic phases at a given distance for specified source depth, with user control over the selection of phases.

ttimes is set up to automatically access the tau-spline tables for the 1991 IASPEI Seismological Tables based on the velocity model iasp91 (direct access files - iasp91.hed, iasp91.tbl). Other sets of tables can be accessed by invoking ttimes with the -model argument (see below).

OPTIONS

The following options are recognized.

-model
    Alternative model to use for calculations (the default is ak135). Choices are ``iasp91'', ``ak135'', ``sp6'', ``kghj'', ``pemc'', ``fakeprem'', ``fakeprem20s''. (PREM-related models are so-named because they contain a crustal structure that is continental, rather than average earth, but the shallow upper mantle structure is slightly modified to yield travel times that differ from PREM by < 0.1s.)

-units
    Distance units, either km or degrees for kilometers or degrees. Default unit is degrees.

-verbose
    A verbose description of the input is provided before input prompts. This is the default behavior.

-terse
    The input isn't described; you are simply prompted for input (phase list, depth and range).

-takeoff
    Add the take-off angle from the focal sphere for each phase to the output listing.

-debug
    Write debugging output to the file ``ttim1.lis''. Only useful for code debugging.

  Phase specification
The phase specification scheme is briefly described when ttimes is run. Initially the specification procedure is set up in query mode and responses need to be made at the star prompt (*), a null response terminates the specification. The selection of phases can be done either by giving a sequence of generic phase names or by specifying keywords. The available keywords are:
P      gives P-up, P, Pdiff, PKP and PKiKP
P+     gives P-up, P, Pdiff, PKP, PKiKP, PcP, pP, pPdiff, pPKP,
             pPKiKP, sP, sPdiff, sPKP, sPKiKP
S      gives S-up, S, Sdiff, SKS
S+     gives S-up, S, Sdiff, SKS, sS, SSdiff, sSKS,
             pS, pSdiff, pSKS
basic  gives P+, S+ and ScP, SKP, PKKP, SKKP, PP and PKPPKP
all    gives all available phases

  Depth specification
Once the choice of phase branches has been made the depth needs to be specified and the specified tau-splines appropriate for that depth are then formed.

  Distance specification
The user is prompted for epicentral distance (delta) and the travel time, slowness, curvature and depth derivative are displayed for each phase.

A new depth can be chosen by setting the distance negative, and the procedure terminated by setting the depth negative as well. End-of-file also stops the program.

ENVIRONMENT

LIBTAUMOD
    If set, specifies an alternative model file name xxxx (for tables xxx.hed, xxx.tbl); identical in function to -model parameter. If first character if name is `/', it is interpreted to mean an absolute path to a file. Otherwise, the model file is sought in the default model directory.

SEE ALSO
gtt91

AUTHORS
R. Buland, National Earthquake Information Centre, U.S. Geological Survey Golden, Colorado
B.L.N. Kennett, Research School of Earth Sciences, Australian National University Canberra, Australia
(extensions by) G. Helffrich, University of Bristol, Earth Sciences, Bristol, UK