grdspotter

grdspotter(cmd0::String="", arg1=nothing; kwargs...)

Create CVA grid from a residual bathymetry or gravity grid.

(Warning: Manual translate by Claude. Needs revision)

Description

grdspotter reads a grid file with residual bathymetry or gravity and calculates flowlines from each node that exceeds a minimum value using the specified rotations file. These flowlines are then convolved with the volume of the prism represented by each grid node and added up to give a Cumulative Volcano Amplitude (CVA) grid [Wessel, 1999; 2008].

Required Arguments

  • ingrid : – Input data grid to be processed (file name or GMTgrid), typically residual bathymetry or free-air anomalies.

  • E or rot or rotations or rot_file : – rotations=“filename” | rotations=“lon/lat/angle”
    Specify the rotation file or a single rotation as "lon/lat/angle". Append +i if you want to invert the finite rotations prior to use.

  • G or outgrid or save : – outgrid=“filename”
    Specify name for output CVA grid file.

  • I or inc or increment or spacing : – inc=x_inc | inc=(x_inc, y_inc) | inc=“xinc[+e|n][/yinc[+e|n]]”
    Specify the grid increments or the block sizes. More at spacing

  • R or region or limits : – limits=(xmin, xmax, ymin, ymax) | limits=(BB=(xmin, xmax, ymin, ymax),) | limits=(LLUR=(xmin, xmax, ymin, ymax),units=“unit”) | …more
    Specify the region of interest. More at limits. For perspective view view, optionally add zmin,zmax. This option may be used to indicate the range used for the 3-D axes. You may ask for a larger w/e/s/n region to have more room between the image and the axes.

Optional Arguments

  • A or agegrid or age_grid : – agegrid=“filename”
    Supply a crustal age grid that is co-registered with the input data grid. These ages become the upper ages to use when constructing flowlines [Default extends flowlines back to oldest age found in the rotation file; but see upper_age].

  • D or DIgrid or PAgrid : – DIgrid=(importance=“file”,) | PAgrid=(predicted=“file”,)
    For importance, we use flowlines to determine the maximum CVA encountered along each flowline and create a Data Importance (DI) grid with these values at the originating nodes. For predicted, we use flowlines to determine the flowline age at the CVA maximum for each node and create a Predicted Age (PA) grid with these values at the originating nodes. Repeatable.

  • L or IDgrid or id_grid : – IDgrid=“filename”
    Supply a co-registered grid with seamount chain IDs for each node. This option requires that you also use IDinfo.

  • M or onthefly or no_memory : – onthefly=true
    Do not attempt to keep all flowlines in memory when using DIgrid and/or PAgrid. Should you run out of memory you can use this option to compute flowlines on-the-fly. It will be slower as we can no longer reuse the flowlines calculated for the CVA step. Cannot be used with bootstrap or the multi-slice mode in zlimits.

  • N or upper_age or maxage : – upper_age=value
    Set the upper age to assign to nodes whose crustal age is unknown (i.e., NaN) [no upper age]. Also see agegrid.

  • Q or IDinfo or id_info : – IDinfo=value | IDinfo=“filename”
    Either give a single ID to use or the name of a file with a list of IDs to use [Default uses all IDs]. Each line would be TAG ID [w e s n]. The w/e/s/n zoom box is optional; if specified it means we only trace the flowline if inside this region. Requires IDgrid.

  • S or normalize or percent : – normalize=true
    Normalize the resulting CVA grid to percentages of the CVA maximum. This also normalizes the DI grid (if requested).

  • T or adjust : – adjust=:truncate | adjust=(truncate=true, fixed=val)
    Selects ways to adjust ages; repeatable. Use truncate=true to truncate crustal ages given via the agegrid option that exceed the upper age set with upper_age [no truncation], or fixed=val which means that after a node passes the test implied by zlimits, we use this fixed_val instead in the calculations [Default uses individual node values].

  • V or verbose : – verbose=true | verbose=level
    Select verbosity level. More at verbose

  • W or bootstrap or ntry : – bootstrap=n
    Get n bootstrap estimates of the maximum CVA location; the longitude and latitude results are written to standard output [Default is no bootstrapping]. Cannot be used with onthefly.

  • Z or zlimits or zrange : – zlimits=zmin | zlimits=(zmin, zmax) | zlimits=(zmin, zmax, zinc)
    Ignore nodes with z-values lower than zmin [0] and optionally larger than zmax [Inf]. Give (zmin, zmax, zinc) to make separate CVA grids for each z-slice [Default makes one CVA grid]. Multi-slicing cannot be used with onthefly.

Notes

GMT distributes the EarthByte rotation model Global_EarthByte_230-0Ma_GK07_AREPS.rot. To use an alternate rotation file, create an environment variable named GPLATES_ROTATIONS that points to an alternate rotation file.

Examples

To create a CVA image from the Pacific topography grid Pac_res_topo.nc, using the DC85.txt Euler poles, and only output a grid for the specified domain:

using GMT
G = grdspotter("Pac_res_topo.nc", rotations="DC85.txt", outgrid="CVA.nc",
               region=(190,220,15,25), inc="2m", upper_age=145, adjust=:truncate)

To also create a Data Importance grid alongside the CVA:

using GMT
G = grdspotter("Pac_res_topo.nc", rotations="DC85.txt", outgrid="CVA.nc",
               region=(190,220,15,25), inc="2m", upper_age=145,
               DIgrid=(importance="DI.nc",), normalize=true)

To get 100 bootstrap estimates of the maximum CVA location:

using GMT
D = grdspotter("Pac_res_topo.nc", rotations="DC85.txt", outgrid="CVA.nc",
               region=(190,220,15,25), inc="2m", bootstrap=100)

References

Wessel, P., 1999, “Hotspotting” tools released, EOS Trans. AGU, 80 (29), p. 319.

Wessel, P., 2008, Hotspotting: Principles and properties of a plate tectonic Hough transform, Geochem. Geophys. Geosyst. 9(Q08004), doi:10.1029/2008GC002058.

See Also