ttimes.1.in

.TH TTIMES 1
.SH NAME
ttimes \- travel time table access using tau-splines
.SH SYNOPSIS
.B ttimes
[ -debug ]
[ -units [ km | deg ]]
[ -verbose | -terse ]
[ -takeoff ]
[ -model \f2name\fP ]
.SH 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.
.LP
ttimes is set up to automatically access the tau-spline tables for a default
model (@@MODNAM@@).
Other sets of tables can be accessed by invoking ttimes
with the -model argument (see below).
.SH OPTIONS
.PP
The following options are recognized.
.IP -model
Alternative model to use for calculations (the default is @@MODNAM@@).
Choices are @@MODELS@@.
(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.)
ss97a and r11dw are Mars seismic velocity models.
.IP -units
Distance units, either \f2km\fP or \f2degrees\fP for kilometers or degrees.
Default unit is degrees.
.IP -verbose
A verbose description of the input is provided before input prompts.
This is the default behavior.
.IP -terse
The input isn't described; you are simply prompted for input (phase list,
depth and range).
.IP -takeoff
Add the take-off angle from the focal sphere for each phase to the output
listing.
.IP -debug
Write debugging output to the file ``ttim1.lis''.
Only useful for code debugging.
.SS 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:
.nf
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
.fi
.SS 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.
.SS Distance specification
The user is prompted for epicentral distance (delta) and the
travel time, slowness, curvature and depth derivative are displayed
for each phase.
.LP 
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.
.SH ENVIRONMENT
.IP LIBTAUMOD
If set, specifies an alternative model file name xxxx (for tables
xxxx.hed, xxxx.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 (@@MDIR@@).
.SH SEE ALSO
gtt91
.SH AUTHORS
R. Buland,
National Earthquake Information Centre, U.S. Geological Survey
Golden, Colorado
.br
B.L.N. Kennett,
Research School of Earth Sciences, Australian National University            
Canberra, Australia 
.br
(extensions by) G. Helffrich,
University of Bristol, Earth Sciences, Bristol, UK