NAME
backtracker - Forward and Backward flowlines and hotspot
tracks
SYNOPSIS
backtracker [infile(s)] -Estage_file [ -A[young/old] ] [ -C
] [ -Df|b ] [ -H[nrec] ] [ -Lf|tstep ] [ -Nupper_age ] [
-Sfilestem ] [ -Tzero_age ] [ -V ] [ -: ] [ -bi[s][n] ] [
-bo[s] ]
DESCRIPTION
backtracker reads (longitude, latitude, age) positions from
infiles [or standard input] and computes projected (x,y,t)
coordinates using the specified stage pole (Euler) rota-
tions. You can either calculate just final positions
[Default] or create a sampled track between initial and
final position. The former mode allows additional data
fields after the first 3 columns which must have
(longitude,latitude,age). See option -: on how to read
(latitude,longitude,age) files.
No space between the option flag and the associated
arguments. Use upper case for the option flags and lower
case for modifiers.
infile(s)
Data file(s) to be projected. If not given, standard
input is read.
-E Give file with stage poles and opening angles. This
file must contain one record for each stage; each
record must be of the following format:
lon lat tstart tstop ccw-angle
where time is in Ma and the rest is in degrees. Oldest
stage must be listed first. tstart is the time when
the stage begins (oldest age). Blank lines and records
whose first column contains # will be ignored.
OPTIONS
-A Used in conjunction with -Lb|f to limit the track out-
put to those sections whose predicted ages fit between
the young and old limits. If -LB|F is used instead
then the limits apply to the stage ids. If not limits
are supplied then individual limits for each seamount
are expected in the input file's columns 4 and 5.
-C Expect Total Reconstruction Poles (Finite Poles) rather
than Backward Stage Poles [Default] File format is
similar to the stage pole format except the youngest
rotation must be listed first and that the tstart
column is optional (assumed to be 0 Ma).
-D Set the direction to go: -Df will go forward in time,
while -Db will go backward in time [Default].
-H Input file(s) has Header record(s). Number of header
records can be changed by editing your .gmtdefaults
file. If used, GMT default is 1 header record.
-L Specify a sampled path between initial and final posi-
tion: -Lf will draw flowlines, while -Lb will draw
backtrack (hotspot track) paths. Append sampling
interval in km. When -LF or -LB is used, the third
output column will contain the stage id (1 is youngest)
[Default is along-track ages].
-N Set the maximum age to extend the oldest stage back in
time [no extension].
-S When -L is set, the tracks are normally written to
stdout as a multisegment file. Specify a filestem to
have each track written to filestem.#, where # is the
track number. The track number is also copied to the
4th output column.
-T Set the current time [0 Ma].
-V Selects verbose mode, which will send progress reports
to stderr [Default runs "silently"].
-: Toggles between (longitude,latitude) and
(latitude,longitude) input/output. [Default is
(longitude,latitude)].
-bi Selects binary input. Append s for single precision
[Default is double]. Append n for the number of
columns in the binary file(s). [Default is 3 input
columns]
-bo Selects binary output. Append s for single precision
[Default is double].
EXAMPLES
To backtrack the (x,y,t) points in the file seamounts.d to
their origin (presumably the hotspot), using the DC85.d
Euler poles, run
backtracker seamounts.d -Db -EDC85.d > newpos.d
To project flowlines forward from the (x,y,t) points stored
in several 3-column, binary, double precision files, run
backtracker points.* -Df -EDC85.d -Lf25 -bo -bi3 > lines.b
This file can then be plotted with psxy -M.
SEE ALSO
gmt(l), project(l), mapproject(l), hotspotter(l)
originator(l)
REFERENCES
Wessel, P., 1999, "Hotspotting" tools released, EOS Trans.
AGU, 80 (29), p. 319.