1GRDSEAMOUNT(1) GMT GRDSEAMOUNT(1)
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6 grdseamount - Compute synthetic seamount (Gaussian or cone, circular or
7 elliptical) bathymetry
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10 grdseamount [ intable ]
11 -Iincrement
12 -Rregion [ -A[out/in] ] [ -Cc|d|g|p ] [ -D[unit] ] [ -E ] [
13 -F[flattening] ] [ -Ggrdfile ] [ -L[cut] ] [ -Mlist ] [ -Nnorm ] [
14 -Qbmode/qmode ] [ -Sscale ] [ -Tt0[u][/t1[u]/dt[u]|n][+l] ] [
15 -Zlevel ] [ -V[level] ] [ -bibinary ] [ -eregexp ] [ -fg ] [ -iflags ]
16 [ -r ]
17 Note: No space is allowed between the option flag and the associated
19 arguments.
20
22 grdseamount will compute the combined shape of multiple synthetic
23 seamounts given their individual shape parameters. We read a list with
24 seamount locations and sizes and can evaluate either Gaussian, parabol‐
25 ic, conical, or disc shapes, which may be circular or elliptical, and
26 optionally truncated. Various scaling options are available to modify
27 the result, including an option to add in a background depth (more com‐
28 plicated backgrounds may be added via grdmath). The input must contain
29 lon, lat, radius, height for each seamount. For elliptical features
30 (-E) we expect lon, lat, azimuth, semi-major, semi-minor, height
31 instead. If flattening is specified (-F) with no value appended then a
32 final column with flattening is expected (cannot be used for plateaus).
33 For temporal evolution of topography the -T option may be used, in
34 which case the data file must have two final columns with the start and
35 stop time of seamount construction. In this case you may choose to
36 write out a cumulative shape or just the increments produced by each
37 time step (see -Q).
38
40 -Ixinc[unit][+e|n][/yinc[unit][+e|n]]
41 x_inc [and optionally y_inc] is the grid spacing. Optionally,
42 append a suffix modifier. Geographical (degrees) coordinates:
43 Append m to indicate arc minutes or s to indicate arc seconds.
44 If one of the units e, f, k, M, n or u is appended instead, the
45 increment is assumed to be given in meter, foot, km, Mile, nau‐
46 tical mile or US survey foot, respectively, and will be con‐
47 verted to the equivalent degrees longitude at the middle lati‐
48 tude of the region (the conversion depends on PROJ_ELLIPSOID).
49 If y_inc is given but set to 0 it will be reset equal to x_inc;
50 otherwise it will be converted to degrees latitude. All coordi‐
51 nates: If +e is appended then the corresponding max x (east) or
52 y (north) may be slightly adjusted to fit exactly the given
53 increment [by default the increment may be adjusted slightly to
54 fit the given domain]. Finally, instead of giving an increment
55 you may specify the number of nodes desired by appending +n to
56 the supplied integer argument; the increment is then recalcu‐
57 lated from the number of nodes and the domain. The resulting
58 increment value depends on whether you have selected a grid‐
59 line-registered or pixel-registered grid; see App-file-formats
60 for details. Note: if -Rgrdfile is used then the grid spacing
61 has already been initialized; use -I to override the values.
62 -Rxmin/xmax/ymin/ymax[+r][+uunit] (more ...)
64 Specify the region of interest.
65
67 -A[out/in]
68 Build a mask grid, append outside/inside values [1/NaN]. Here,
69 height is ignored and -L, -N and -Z are disallowed.
70 -C Select shape function: choose among c (cone), d (disc), g
72 (Gaussian) and p (parabolic) shape [Default is Gaussian].
73 -Dunit Append the unit used for horizontal distances in the input file
75 (see UNITS). Does not apply for geographic data (-fg) which we
76 convert to km.
77 -E Elliptical data format. We expect the input records to contain
79 lon, lat, azimuth, major, minor, height (with the latter in m)
80 for each seamount. [Default is Circular data format, expecting
81 lon, lat, radius, height].
82 -F[flattening]
84 Seamounts are to be truncated to guyots. Append flattening,
85 otherwise we expect to find it in last input column [no trunca‐
86 tion]. Ignored if used with -Cd.
87 -Ggrdfile
89 Specify the name of the output grid file; see GRID FILE FORMATS
90 below). If -T is set then grdfile must be a filename template
91 that contains a floating point format (C syntax). If the file‐
92 name template also contains either %s (for unit name) or %c (for
93 unit letter) then we use the corresponding time (in units speci‐
94 fied in -T) to generate the individual file names, otherwise we
95 use time in years with no unit.
96 -L[cut]
98 List area, volume, and mean height for each seamount; No grid is
99 created. Optionally, append the noise-floor cutoff level below
100 which we ignore area and volume [0].
101 -Mlist Write the names of all grids that were created to the text file
103 list. Requires -T.
104 -Nnorm Normalize grid so maximum grid height equals norm.
106 -Qbmode/qmode
108 Only to be used in conjunction with -T. Append two different
109 modes settings: The bmode determines how we construct the sur‐
110 face. Specify c for cumulative volume through time, or i for
111 incremental volume added for each time slice. The qmode deter‐
112 mines the volume flux curve. Give g for a Gaussian volume flux
113 history or l for a linear volume flux history between the start
114 and stop times of each feature.
115 -Sscale
117 Sets optional scale factor for radii [1].
118 -Tt0[u][/t1[u]/dt[u]|n][+l]
120 Specify t0, t1, and time increment (dt) for sequence of calcula‐
121 tions [Default is one step, with no time dependency]. For a
122 single specific time, just give start time t0. The unit is
123 years; append k for kyr and M for Myr. For a logarithmic time
124 scale, append +l and specify n steps instead of dt. Alterna‐
125 tively, give a file with the desired times in the first column
126 (these times may have individual units appended, otherwise we
127 assume year). Note that the grid for t0 (if a range is given)
128 is not written as it is zero and marks the start of the building
129 history.
130 -Zlevel
132 Set the background depth [0].
133 -bi[ncols][t] (more ...)
135 Select native binary input. [Default is 4 input columns].
136 -e[~]"pattern" | -e[~]/regexp/[i] (more ...)
138 Only accept data records that match the given pattern.
139 -fg Geographic grids (dimensions of longitude, latitude) will be
141 converted to km via a "Flat Earth" approximation using the cur‐
142 rent ellipsoid parameters.
143 -h[i|o][n][+c][+d][+rremark][+rtitle] (more ...)
145 Skip or produce header record(s). Not used with binary data.
146 -icols[+l][+sscale][+ooffset][,...] (more ...)
148 Select input columns and transformations (0 is first column).
149 -V[level] (more ...)
151 Select verbosity level [c].
152 -r (more ...)
154 Set pixel node registration [gridline].
155 -:[i|o] (more ...)
157 Swap 1st and 2nd column on input and/or output.
158 -^ or just -
160 Print a short message about the syntax of the command, then
161 exits (NOTE: on Windows just use -).
162 -+ or just +
164 Print an extensive usage (help) message, including the explana‐
165 tion of any module-specific option (but not the GMT common
166 options), then exits.
167 -? or no arguments
169 Print a complete usage (help) message, including the explanation
170 of all options, then exits.
171
173 For map distance unit, append unit d for arc degree, m for arc minute,
174 and s for arc second, or e for meter [Default], f for foot, k for km, M
175 for statute mile, n for nautical mile, and u for US survey foot. By
176 default we compute such distances using a spherical approximation with
177 great circles. Prepend - to a distance (or the unit is no distance is
178 given) to perform "Flat Earth" calculations (quicker but less accurate)
179 or prepend + to perform exact geodesic calculations (slower but more
180 accurate).
181
183 To compute the incremental loads from two elliptical, truncated Gauss‐
184 ian seamounts being constructed from 3 Ma to 2 Ma and 2.8 M to 1.9 Ma
185 using a linear volumetric production rate, and output an incremental
186 grid every 0.1 Myr from 3 Ma to 1.9 Ma, we can try:
187 cat << EOF > t.txt
189 #lon lat azimuth, semi-major, semi-minor, height tstart tend
190 0 0 -20 120 60 5000 3.0M 2M
191 50 80 -40 110 50 4000 2.8M 21.9M
192 EOF
193 gmt grdseamount -Rk-1024/1022/-1122/924 -I2000 -Gsmt_%3.1f_%s.nc t.txt -T3M/1.9M/0.1M -Qi/l -Dk -E -F0.2 -Cg -Ml.lis
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196 gmt.conf, gmt, grdmath, gravfft, gmtflexure
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199 2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
2005.4.5 Feb 24, 2019 GRDSEAMOUNT(1)