grdpmodeler(1) GMT grdpmodeler(1)
NAME
grdpmodeler - Evaluate a plate motion model on a geographic grid
SYNOPSIS
grdpmodeler agegrdfile -Erot_file -Sflags [ -Fpolygonfile ] [ -Gout-
grdfile ] [ -Tage ] [ -V[level] ] [ -bbinary ] [ -dnodata ] [ -hhead-
ers ] [ -:[i|o] ]
Note: No space is allowed between the option flag and the associated
arguments.
DESCRIPTION
grdpmodeler reads a geographical age grid and a plate motion model and
evaluates one of several model predictions. Optionally, the user may
supply a clipping polygon in multiple-segment format; then, only the
part of the grid inside the polygon is used to determine the model pre-
diction; the remainder of the grid is set to NaN.
REQUIRED ARGUMENTS
ingrdfile
Name of a grid file in geographical (lon, lat) coordinates with
ages in Myr.
-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.
-Sflags
Type of model prediction(s). Append one or more items: choose
from a for plate motion azimuth, d for great-circle distance
between current location and its origin at the ridge (in km), s
for plate motion model stage ID (1 is youngest), v for plate
motion rate (in mm/yr), w for plate rotation rate (degree/Myr),
x for change in longitude relative to location of crust forma-
tion, y for change in latitude relative to location of crust
formation, X for longitude of crust formation, and Y for lati-
tude of crust formation. If no arguments are given we default
to all [adsvwxyXY].
OPTIONAL ARGUMENTS
-Fpolygonfile
Specify a multisegment closed polygon file that describes the
inside area of the grid where the model should be evaluated; the
outside will be set to NaN [Default evaluates model on the
entire grid].
-Goutgrdfile
Name of output grid. This is the grid with the model predictions
given the specified rotations. Note: If you specified more than
one model prediction in -S then the filename must be a template
that contains the format %s; this will be replaced with the cor-
responding tags az, dist, stage, vel, omega, dlon, dlat, lon,
lat. If the -G option is not used then we create no grids and
instead write lon, lat, age, predictions records to standard
output.
-Tage Use a fixed age for model evaluation (i.e., override the ages in
the age grid). This lets you evaluate the model at a snapshot in
time.
-V[level] (more a|)
Select verbosity level [c].
-bi[ncols][t] (more a|)
Select native binary input. [Default is 2 input columns].
-d[i|o]nodata (more a|)
Replace input columns that equal nodata with NaN and do the
reverse on output.
-h[i|o][n][+c][+d][+rremark][+rtitle] (more a|)
Skip or produce header record(s).
-^ 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
We will use a grid with Pacific crust ages (pac_age.nc), a plate motion
model (Pac_APM.d), and a polygon that contains the outline of the
present Pacific plate (pac_clip_path.d). To evaluate the plate motion
azimuths at the present time for the Pacific, try
gmt grdpmodeler pac_age.nc -EPac_APM.d -V -Fpac_clip_path.d \
-Gpac_dir_0.nc -Sa -T0
To determine the changes in latitude since crust formation for the
entire Pacific, try
gmt grdpmodeler pac_age.nc -EPac_APM.d -V -Fpac_clip_path.d \
-Gpac_dlat.nc -Sy
To determine the plate motion velocities in effect when the Pacific
crust was formed, try
gmt grdpmodeler pac_age.nc -EPac_APM.d -V -Fpac_clip_path.d \
-Gpac_vel.nc -Sv
To determine how far the crust has moved since formation, try
gmt grdpmodeler pac_age.nc -EPac_APM.d -V -Fpac_clip_path.d \
-Gpac_dist.nc -Sd
To save the coordinates of the crustas formation to separate grids, try
gmt grdpmodeler pac_age.nc -EPac_APM.d -V -Fpac_clip_path.d \
-Gpac_origin_%s.nc -SXY
To repeat the same exercise but save output lon,lat,age,xorigin,yorigin
to a table, use
gmt grdpmodeler pac_age.nc -EPac_APM.d -V -Fpac_clip_path.d -SXY > origin.txt
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
backtracker(1), gmtpmodeler(1), grdrotater(1), grdspotter(1),
hotspotter(1), originator(1), rotconverter(1)
COPYRIGHT
2017, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
5.4.2 Jun 24, 2017 grdpmodeler(1)
gmt5 5.4.2 - Generated Thu Jun 29 07:41:12 CDT 2017