originatorgmt - Online in the Cloud

PROGRAM:

NAME

originator - Associate seamounts with nearest hotspot point sources

SYNOPSIS

originator [ tables ] [+]rotfile [+]hs_file [ d_km ] [ [flag] ] [ upper_age ] [ r/t ] [
[n_hs] ] [ ] [ [level] ] [ maxdist ] [ ] [ -bi<binary> ] [ -di<nodata> ] [ -h<headers> ]
[ -i<flags> ] [ -:[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 rotation cannot be found. Prepend + if you want to invert the
rotations 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 represents the minimal
hotspot information record type. The abbreviation 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 programs 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
location 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 ...)
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 ...)
Select native binary input. [Default is 5 input columns].

-dinodata (more ...)
Replace input columns that equal nodata with NaN.

-V[level] (more ...)
Select verbosity level [c].

-icols[l][sscale][ooffset][,...] (more ...)
Select input columns (0 is first column).

-:[i|o] (more ...)
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
use just -).

-+ or just +
Print an extensive usage (help) message, including the explanation 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 options, then
exits.

--version
Print GMT version and exit.

--show-datadir
Print full path to GMT share directory and exit.

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 coordinates. 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 closest approach was east
of the hotspot.

NOTES

GMT distributes the EarthByte rotation model Global_EarthByte_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.

Use originatorgmt online using onworks.net services