coupe¶

Plot cross-sections of focal mechanisms

Synopsis¶

gmt coupe [ table ] -Jparameters -Rregion -Aparameters -Sformat[scale][+aangle][+ffont][+jjustify][+odx[/dy]] [ -B[p|s]parameters ] [ -Ccpt ] [ -Efill ] [ -Fmode[args] ] [ -Gfill ] [ -H[scale] ] [ -I[intens] ] [ -L[pen] ] [ -M ] [ -N ] [ -Q ] [ -Tnplane[/pen] ] [ -U[stamp] ] [ -V[level] ] [ -Wpen ] [ -X[a|c|f|r][xshift] ] [ -Y[a|c|f|r][yshift] ] [ -dinodata ] [ -eregexp ] [ -hheaders ] [ -iflags ] [ -pflags ] [ -qiflags ] [ -ttransp ] [ -:[i|o] ] [ --PAR=value ]

Note: No space is allowed between the option flag and the associated arguments.

Description¶

Reads data values from table [or standard input] and will plot a cross-section of focal mechanisms. The name “coupe” comes from the French verb “to cut”. The best translation is a (vertical) cross section.

Unless -Q is used, new file is created with the new coordinates (x, y) and the mechanism (from lower focal half-sphere for horizontal plane, to half-sphere behind a vertical plane). When the plane is not horizontal, - north direction becomes upwards steepest descent direction of the plane (u) - east direction becomes strike direction of the plane (s) - down direction (= north^east) becomes u^s Axis angles are defined in the same way as in horizontal plane in the new system. Moment tensor (initially in r, t, f system that is up, south, east) is defined in (-u^s, -u, s) system.

Required 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.

-Jparameters

Specify the projection. (See full description) (See cookbook summary) (See projections table).

-Rwest/east/south/north[/zmin/zmax][+r][+uunit]

west, east, south, and north specify the region of interest, and you may specify them in decimal degrees or in [±]dd:mm[:ss.xxx][W|E|S|N] format Append +r if lower left and upper right map coordinates are given instead of w/e/s/n. The two shorthands -Rg and -Rd stand for global domain (0/360 and -180/+180 in longitude respectively, with -90/+90 in latitude). Set geographic regions by specifying ISO country codes from the Digital Chart of the World using -Rcode1,code2,…[+r|R[incs]] instead: Append one or more comma-separated countries using the 2-character ISO 3166-1 alpha-2 convention. To select a state of a country (if available), append .state, e.g, US.TX for Texas. To specify a whole continent, prepend = to any of the continent codes AF (Africa), AN (Antarctica), AS (Asia), EU (Europe), OC (Oceania), NA (North America), or SA (South America). Use +r to modify the bounding box coordinates from the polygon(s): Append inc, xinc/yinc, or winc/einc/sinc/ninc to adjust the region to be a multiple of these steps [no adjustment]. Alternatively, use +R to extend the region outward by adding these increments instead, or +e which is like +r but it ensures that the bounding box extends by at least 0.25 times the increment [no extension]. Alternatively for grid creation, give Rcodelon/lat/nx/ny, where code is a 2-character combination of L, C, R (for left, center, or right) and T, M, B for top, middle, or bottom. e.g., BL for lower left. This indicates which point on a rectangular region the lon/lat coordinate refers to, and the grid dimensions nx and ny with grid spacings via -I is used to create the corresponding region. Alternatively, specify the name of an existing grid file and the -R settings (and grid spacing and registration, if applicable) are copied from the grid. Appending +uunit expects projected (Cartesian) coordinates compatible with chosen -J and we inversely project to determine actual rectangular geographic region. For perspective view (-p), optionally append /zmin/zmax. In case of perspective view (-p), a z-range (zmin, zmax) can be appended to indicate the third dimension. This needs to be done only when using the -Jz option, not when using only the -p option. In the latter case a perspective view of the plane is plotted, with no third dimension. If frame is defined from cross-section parameters (see -A this option is not taken into account, but must be present.

-A

Select the cross-section parameters:

-Aalon1/lat1/lon2/lat2[+ddip][+wwidth][+zdmin/dmax][+r]

lon and lat are the longitude and latitude of points 1 and 2 limiting the length of the cross-section, dip is the dip of the plane on which the cross-section is made [90], width is the width in km of the cross-section on each side of a vertical plane or above and under an oblique plane [infinity], and dmin and dmax are the distances min and max from horizontal plane in km, along steepest descent direction. Add +r to get the plot domain from the cross-section parameters.

-Ablon1/lat1/strike/length[+ddip][+wwidth][+zdmin/dmax][+r]

lon1 and lat1 are the longitude and latitude of the beginning of the cross-section, strike is the azimuth of the direction of the cross-section, and length is the length along which the cross-section is made (in km). The other parameters are the same as for -Aa option.

-Acx1/y1/x2/y2[+ddip][+wwidth][+zdmin/dmax][+r]

The same as -Aa option with x and y given as Cartesian coordinates.

The same as -Ab option with x and y given as Cartesian coordinates.

-Sformat[scale][+aangle][+ffont][+jjustify][+odx[/dy]]

Selects the meaning of the columns in the data file. scale adjusts the scaling of the radius of the “beach ball”, which will be proportional to the magnitude. scale is the size for magnitude = 5 (i.e. scalar seismic moment M0 = 4.0E23 dynes-cm). The color or shade of the compressive quadrants can be specified with the -G option. The color or shade of the extensive quadrants can be specified with the -E option. For each beachball, a text string can be specified to appear near the beachball [optional]. Append +aangle to change the angle of the text string; append +ffont to change its font (size,fontname,color); append +jjustify to change the text location relative to the beachball (default is above the beachball); append +o to offset the text string by dx/dy. Note: If scale is missing then we expect to read this value from the data record via the first column after the required columns for the symbol type.

In order to use the same file to plot cross-sections, depth is in third column. Nevertheless, it is possible to use “old style” psvelomeca input files without depth in third column using the -Fo option.

-Sa[scale][+ffont][+jjustify][+odx[/dy]]

Focal mechanisms in Aki and Richards convention. Parameters are expected to be in the following columns:

1,2: longitude, latitude of event (-: option interchanges order)

3: depth of event in kilometers

4,5,6: strike, dip and rake in degrees

7: magnitude

8,9: longitude, latitude at which to place beachball if -A is used (optional). Using 0,0 in columns 8 and 9 will plot the beach ball at the longitude, latitude given in columns 1 and 2. The -: option will interchange the order of columns (1,2) and (8,9).

10: Text string to appear near the beach ball (optional).

-Sc[scale][+ffont][+jjustify][+odx[/dy]]

Focal mechanisms in Global CMT convention. Parameters are expected to be in the following columns:

1,2: longitude, latitude of event (-: option interchanges order)

3: depth of event in kilometers

4,5,6: strike, dip, and rake of plane 1

7,8,9: strike, dip, and rake of plane 2

10,11: mantissa and exponent of moment in dyne-cm

12,13: longitude, latitude at which to place beachball if -A is used (optional). Using 0,0 in columns 12 and 13 will plot the beach ball at the longitude, latitude given in columns 1 and 2. The -: option will interchange the order of columns (1,2) and (12,13).

14: Text string to appear near the beach ball (optional).

-Sm|d|z[scale][+ffont][+jjustify][+odx[/dy]]

Seismic moment tensor. -Sm plots the full seismic moment tensor. -Sz plots the deviatoric part of the moment tensor (zero trace). -Sd plots the closest double couple defined from the moment tensor (zero trace and zero determinant). Global CMT moment tensors are deviatoric, so -Sm and -Sz will produce the same result, but -Sd will not, unless the input moment tensor is already a double couple. Parameters are expected to be in the following columns:

1,2: longitude, latitude of event (-: option interchanges order)

3: depth of event in kilometers

4,5,6,7,8,9: mrr, mtt, mff, mrt, mrf, mtf in 10*exponent dynes-cm

10: exponent

11,12: longitude, latitude at which to place beachball if -A is used (optional). Using 0,0 in columns 11 and 12 will plot the beach ball at the longitude, latitude given in columns 1 and 2. The -: option will interchange the order of columns (1,2) and (11,12).

13: Text string to appear near the beach ball (optional).

-Sp[scale][+ffont][+jjustify][+odx[/dy]]

Focal mechanisms given with partial data on both planes. Parameters are expected to be in the following columns:

1,2: longitude, latitude of event (-: option interchanges order)

3: depth of event in kilometers

4,5: strike, dip of plane 1

6: strike of plane 2

7: must be -1/+1 for a normal/inverse fault

8: magnitude

9,10: longitude, latitude at which to place beachball if -A is used (optional). Using 0,0 in columns 9 and 10 will plot the beach ball at the longitude, latitude given in columns 1 and 2. The -: option will interchange the order of columns (1,2) and (9,10).

11: Text string to appear near the beach ball (optional).

-Sx|y|t[scale][+ffont][+jjustify][+odx[/dy]]

Principal axis. Use -Sx to plot full seismic moment tensor. Use -Sy to plot the closest double couple defined from the moment tensor (zero trace and zero determinant). Use -St to plot the deviatoric part of the moment tensor (zero trace). Parameters are expected to be in the following columns:

1,2: longitude, latitude of event (-: option interchanges order)

3: depth of event in kilometers

4,5,6,7,8,9,10,11,12: value (in 10*exponent dynes-cm), azimuth, plunge of T, N, P axis.

13: exponent

14,15: longitude, latitude at which to place beachball if -A is used (optional). Using 0,0 in columns 14 and 15 will plot the beach ball at the longitude, latitude given in columns 1 and 2. The -: option will interchange the order of columns (1,2) and (14,15).

16: Text string to appear near the beach ball (optional).

Optional Arguments¶

-B[p|s]parameters

Set map boundary frame and axes attributes. (See full description) (See cookbook information).

-Ccpt

Give a CPT and let compressive part color be determined by the z-value in the third column.

-Efill (more …)

Set color or fill pattern for extensive quadrants [Default is white].

-Fmode[args]

Set one or more attributes; repeatable. The various combinations are

-Fssymbol[size][+ffont][+jjustify][+odx[/dy]]

Select a symbol instead of mechanism. Choose from the following: (c) circle, (d) diamond, (i) itriangle, (s) square, (t) triangle, (x) cross. size is the symbol size in PROJ_LENGTH_UNIT (unless c, i, or p is appended to indicate that the size information is in units of cm, inches, meters, or points, respectively). If size must be read, it must be in column 4 and the text string will start in column 5.

Append +ffont to change the font of the text string; append +jjustify to change the text location relative to the beachball (default is above the beachball); append +o to offset the text string by dx/dy.

Parameters are expected to be in the following columns:

1,2:

longitude, latitude of event (-: option interchanges order)

3:

depth of event in kilometers

4:

Text string to appear near the beach ball

-Fa[size[/Psymbol[Tsymbol]]]

Compute and plot P and T axes with symbols. Optionally specify size and (separate) P and T axis symbols from the following: (c) circle, (d) diamond, (h) hexagon, (i) inverse triangle, (p) point, (s) square, (t) triangle, (x) cross. [Default: 6p/cc]

-Fefill (more …)

Set the color or fill pattern for the T axis symbol. [Default as set by -E]

-Fgfill (more …)

Set the color or fill pattern for the P axis symbol. [Default as set by -G]

-Fp[pen]

Draw the P axis outline using current pen (see -W), or sets pen attributes.

-Fr[fill]

Draw a box behind the label (if any). [Default fill is white]

-Ft[pen]

Draw the T axis outline using current pen (see -W), or sets pen attributes.

-Gfill (more …)

Set color or fill pattern for compressional quadrants [Default is black].

-H[scale]

Scale symbol sizes and pen widths on a per-record basis using the scale read from the data set, given as the first column after the (optional) size columns [no scaling]. The symbol size is either provided by -S or via the input size column. Alternatively, append a constant scale that should be used instead of reading a scale column.

-Iintens

Use the supplied intens value (nominally in the -1 to +1 range) to modulate the compressional fill color by simulating illumination [none]. If no intensity is provided we will instead read intens from an extra data column after the required input columns determined by -S.

-L[pen]

Draw the “beach ball” outline using current pen (see -W) or sets pen attributes.

-M

Same size for any magnitude.

-N

Does NOT skip symbols that fall outside map border [Default plots points inside border only].

-Q

Suppress the production of files with cross-section and mechanism information.

-T[nplane][/pen]

Plot the nodal planes and outlines the bubble which is transparent. If nplane is

0: both nodal planes are plotted;

1: only the first nodal plane is plotted;

2: only the second nodal plane is plotted.

Append /pen to set the pen attributes for this feature. Default pen is as set by -W. [Default: 0].

For double couple mechanisms, the -T option renders the beach ball transparent by drawing only the nodal planes and the circumference. For non-double couple mechanisms, -T0 option overlays best double couple transparently.

-U[label|+c][+jjust][+odx/dy]

Draw GMT time stamp logo on plot. (See full description) (See cookbook information).

-V[level]

Select verbosity level [w]. (See full description) (See cookbook information).

-W[pen] (more …)

Set pen attributes for text string or default pen attributes for fault plane edges. [Defaults: default,black,solid].

-X[a|c|f|r][xshift]

Shift plot origin. (See full description) (See cookbook information).

-Y[a|c|f|r][yshift]

Shift plot origin. (See full description) (See cookbook information).

-dinodata (more …)

Replace input columns that equal nodata with NaN.

-e[~]“pattern” | -e[~]/regexp/[i] (more …)

Only accept data records that match the given pattern.

-icols[+l][+ddivide][+sscale][+ooffset][,][,t[word]] (more …)

Select input columns and transformations (0 is first column, t is trailing text, append word to read one word only).

-p[x|y|z]azim[/elev[/zlevel]][+wlon0/lat0[/z0]][+vx0/y0] (more …)

Select perspective view.

-qi[~]rows[+ccol][+a|f|s] (more …)

Select input rows or data range(s) [default is all rows].

-t[transp[/transp2]][+f][+s]

Set transparency level for an overlay, in [0-100] percent range. [Default is 0, i.e., opaque]. Only visible when PDF or raster format output is selected. Only the PNG format selection adds a transparency layer in the image (for further processing). If given, transp applies to both fill and stroke, but you can limit the transparency to one of them by appending +f or +s for fill or stroke, respectively. Alternatively, append /transp2 to set separate transparencies for fills and strokes. If no transparencies are given then we expect to read them from the last numerical column(s). Use the modifiers to indicate which one(s) we should be reading (if both are requested, fill transparency is expected before stroke transparency in the column order). If just -t is given then we interpret it to mean -t+f for fill transparency only.

-:[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 exit (NOTE: on Windows just use -).

-+ or just +

Print an extensive usage (help) message, including the explanation of any module-specific option (but not the GMT common options), then exit.

-? or no arguments

Print a complete usage (help) message, including the explanation of all options, then exit.

--PAR=value

Temporarily override a GMT default setting; repeatable. See gmt.conf for parameters.

Data Column Order¶

The -S option determines how many size columns are required to generate the selected symbol, but if size is not given then we expect to read size from file. In addition, your use of options -H, -I and -t will require extra columns. The order of the data record is fixed regardless of option order, even if not all items may be activated. We expect data columns to come in the following order:

```lon lat depth symbol-columns [size] [scale] [intens] [transp [transp2]] [trailing-text]
```

where items given in brackets are optional and under the control of the stated options: -S without a size selects the optional size-columns, -H selects the optional scale column, -I selects the optional intens column, and -t selects the optional transp column(s). Trailing text is always optional. Notes: (1) depth is normally required but will not be expected if -Fo is given to meca. (2) You can use -i to rearrange your data record to match the expected format.

References¶

• Aki, K., & Richards, P. G. (1980). Quantitative seismology: theory and methods. San Francisco: W. H. Freeman.

• Dahlen, F. A., & Tromp, J. (1998). Theoretical global seismology. Princeton, N.J: Princeton University Press.

• Frohlich, C. (1996). Cliff’s Nodes Concerning Plotting Nodal Lines for P, SH and SV. Seismological Research Letters, 67(1), 16–24. https://doi.org/10.1785/gssrl.67.1.16

• Lay, T., & Wallace, T. C. (1995). Modern global seismology. San Diego: Academic Press.

Author¶

Genevieve Patau, Laboratory of Seismogenesis, Institut de Physique du Globe de Paris, Departement de Sismologie, Paris, France