originator(1) GMT originator(1)
NAME
originator - Associate seamounts with nearest hotspot point sources
SYNOPSIS
originator [ tables ] -E[+]rotfile
-F[+]hs_file [ -Dd_km ] [ -L[flag] ] [ -Nupper_age ] [ -Qr/t ] [
-S[n_hs] ] [ -T ] [ -V[level] ] [ -Wmaxdist ] [ -Z ] [ -bibinary ]
[ -dinodata ] [ -eregexp ] [ -hheaders ] [ -iflags ] [ -:[i|o] ]
Note: No space is allowed between the option flag and the associated
arguments.
DESCRIPTION
originator reads (longitude, latitude, height, radius, crustal_age)
records from tables [or standard input] and uses the given Absolute
Plate Motion (APM) stage or total reconstruction rotation file and the
list of hotspot locations to determine the most likely origin (hotspot)
for each seamount. It does so by calculating flowlines back in time and
determining the closest approach to all hotspots. The output consists
of the input records with four additional fields added for each of the
n_hs closest hotspots. The four fields are the hotspot id (e.g., HWI),
the stage id of the flowline segment that came closest, the pseudo-age
of the seamount, and the closest distance to the hotspot (in km). See
option -: on how to read (latitude, longitude,height, radius,
crustal_age) files.
REQUIRED ARGUMENTS
-Erotfile
Give file with rotation parameters. This file must contain one
record for each rotation; each record must be of the following
format:
lon lat tstart [tstop] angle [ khat a b c d e f g df ]
where tstart and tstop are in Myr and lon lat angle are in
degrees. tstart and tstop are the ages of the old and young ends
of a stage. If tstop is not present in the record then a total
reconstruction rotation is expected and tstop is implicitly set
to 0 and should not be specified for any of the records in the
file. If a covariance matrix C for the rotation is available it
must be specified in a format using the nine optional terms
listed in brackets. Here, C = (g/khat)*[ a b d; b c e; d e f ]
which shows C made up of three row vectors. If the degrees of
freedom (df) in fitting the rotation is 0 or not given it is set
to 10000. Blank lines and records whose first column contains #
will be ignored. You may prepend a leading + to the filename to
indicate you wish to invert the rotations. Alternatively, give
the filename composed of two plate IDs separated by a hyphen
(e.g., PAC-MBL) and we will instead extract that rotation from
the GPlates rotation database. We return an error if the rota-
tion cannot be found. Prepend + if you want to invert the rota-
tions prior to use.
-Ffile Give file with hotspot locations. This file must contain one
record for each hotspot to be considered; each record must be of
the following format:
lon lat hs_abbrev hs_id r t_off t_on create fit plot name
E.g., for Hawaii this may look like
205 20 HWI 1 25 0 90 Y Y Y Hawaii
Most applications only need the first 4 columns which thus rep-
resents the minimal hotspot information record type. The abbre-
viation may be maximum 3 characters long. The id must be an
integer from 1-32. The positional uncertainty of the hotspot is
given by r (in km). The t_off and t_on variables are used to
indicate the active time-span of the hotspot. The create, fit,
and plot indicators are either Y or N and are used by some pro-
grams to indicate if the hotspot is included in the ID-grids
used to determine rotations, if the hotspot chain will be used
to determine rotations, and if the hotspot should be included in
various plots. The name is a 32-character maximum text string
with the full hotspot name. Blank lines and records whose first
column contains # will be ignored. Prepend + if we should look
for hotspot drift tables whose name must be hs_abbrev_drift.txt.
Such files may be located in the current directory, the same
directory as hs_file, or in the directories pointed to by
GMT_DATADIR. If found then we interpolate to get hotspot loca-
tion as a function of time [fixed].
OPTIONAL ARGUMENTS
table One or more ASCII (or binary, see -bi[ncols][type]) data table
file(s) holding a number of data columns. If no tables are given
then we read from standard input.
-Dd_km Sets the flowline sampling interval in km. [Default is 5].
-L[flag]
Output closest approach for nearest hotspot only (ignores -S).
Choose -Lt for (time, dist, z) [Default], -Lw for (omega, dist,
z), and -Ll for (lon, lat, time, dist, z). Normally, dist is in
km; use upper case modifiers TWL to get dist in spherical
degrees.
-Nupper_age
Set the maximum age to extend the oldest stage back in time [no
extension].
-Qr/t Input files only has (x,y,z); specify constant values for r,t
that will be implied for each record.
-S[n_hs]
Set the number of closest hotspots to report [Default is 1].
-T Truncate seamount ages exceeding the upper age set with -N [no
truncation].
-V[level] (more a|)
Select verbosity level [c].
-Wmaxdist
Only report those seamounts whose flowlines came within maxdist
to any hotspot [Default reports all seamounts].
-Z Use the hotspot ID number rather than the name tag in output
records.
-bi[ncols][t] (more a|)
Select native binary input. [Default is 5 input columns].
-dinodata (more a|)
Replace input columns that equal nodata with NaN.
-e[~]^<i>apattern^<i>a | -e[~]/regexp/[i] (more a|)
Only accept data records that match the given pattern.
-V[level] (more a|)
Select verbosity level [c].
-icols[+l][+sscale][+ooffset][,^<i>a|] (more a|)
Select input columns and transformations (0 is first column).
-:[i|o] (more a|)
Swap 1st and 2nd column on input and/or output.
-^ or just -
Print a short message about the syntax of the command, then
exits (NOTE: on Windows just use -).
-+ or just +
Print an extensive usage (help) message, including the explana-
tion of any module-specific option (but not the GMT common
options), then exits.
-? or no arguments
Print a complete usage (help) message, including the explanation
of all options, then exits.
GEODETIC VERSUS GEOCENTRIC COORDIINATES
All spherical rotations are applied to geocentric coordinates. This
means that incoming data points and grids are considered to represent
geodetic coordinates and must first be converted to geocentric coordi-
nates. Rotations are then applied, and the final reconstructed points
are converted back to geodetic coordinates. This default behavior can
be bypassed if the ellipsoid setting PROJ_ELLIPSOID is changed to
Sphere.
EXAMPLES
To find the likely (hotspot) origins of the seamounts represented by
the (x,y,z,r,tc) points in the file seamounts.d, using the DC85.d Euler
poles and the pac_hs.d list of possible hotspots, and report the 2 most
likely hotspot candidates for each seamount, run
gmt originator seamounts.d -S2 -EDC85.d -Fpac_hs.d > origins.d
To determine the predicted age of a seamount, distances to the closest
hotspot, and echo the observed age given its location, observed age,
and a rotation model, try
echo "1.55 -8.43 52.3" | gmt originator -FONeill_2005_hotspots.txt \
-EOMS2005_APM_fixed.txt -Q1/120 -Lt
where 52.3 Ma is observed age. The output is 70 -95.486 52.3. To repeat
the same exercise with a moving hotspot model, try
echo "1.55 -8.43 52.3" | gmt originator -F+ONeill_2005_hotspots.txt \
-EOMS2005_APM_smooth.txt -Q1/120 -Lt
Now the output is 80 -213.135 52.3. Negative distances means the clos-
est approach was east of the hotspot.
NOTES
GMT distributes the EarthByte rotation model Global_Earth-
Byte_230-0Ma_GK07_AREPS.rot. To use an alternate rotation file, create
an environmental parameters named GPLATES_ROTATIONS that points to an
alternate rotation file.
SEE ALSO
gmt(1), grdrotater(1), grdspotter(1), project(1), mapproject(1),
backtracker(1), gmtpmodeler(1), grdpmodeler(1), grdrotater(1),
hotspotter(1)
REFERENCES
Wessel, P., 1999, aHotspottinga tools released, EOS Trans. AGU, 80
(29), p. 319.
COPYRIGHT
2017, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
5.4.2 Jun 24, 2017 originator(1)
gmt5 5.4.2 - Generated Thu Jun 29 14:53:27 CDT 2017