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MECA(1gmt) GMT MECA(1gmt)

NAME

meca - Plot focal mechanisms on maps

SYNOPSIS

gmt meca [ table ] -Jparameters -Rregion
-S<format><scale>[+ffont][+jjustify][+odx[/dy]] [ -B[p|s]parameters ] [ -C[pen][+spointsize] ] [ -Ddepmin/depmax ] [ -Efill] [ -Fmode[args] ] [ -Gfill] [ -L[pen] ] [ -M ] [ -N ] [ -Tnplane[/pen] ] [ -U[stamp] ] [ -V[level] ] [ -Wpen ] [ -X[a|c|f|r][xshift[u]] ] [ -Y[a|c|f|r][yshift[u]] ] [ -Zcpt] [ -dinodata ] [ -eregexp ] [ -hheaders ] [ -iflags ] [ -pflags ] [ -ttransp ] [ -:[i|o] ] [ --PAR=value ]

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

DESCRIPTION

Reads data values from files [or standard input] and will plot focal mechanisms on a map. Many options are similar to those of plot.

REQUIRED ARGUMENTS

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.

Select map projection.

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 [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, 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.

-S<format><scale>[+ffont][+jjustify][+odx[/dy]]

Selects the meaning of the columns in the data file. 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.


-Sascale[+ffont][+jjustify][+odx[/dy]]

Focal mechanisms in Aki and Richards convention. 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. Use the -T option to render the beach ball transparent by drawing only the nodal planes and the circumference. 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. Append +u to have the text appear below the beach ball (default is above). 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 beach ball. Entries in these columns are necessary with the -C option. 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 above or below the beach ball (optional).



-Scscale[+ffont][+jjustify][+odx[/dy]]

Focal mechanisms in Global CMT convention. 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 (that is M0 = 4.0E23 dynes-cm). Use the -T option to render the beach ball transparent by drawing only the nodal planes and the circumference. 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. Append +u to have the text appear below the beach ball (default is above). 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 beach ball. Entries in these columns are necessary with the -C option. 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 above or below the beach ball (optional).



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

Seismic moment tensor (Global CMT, with zero trace). 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 (that is scalar seismic moment = 4.0E23 dynes-cm). -T0 option overlays best double couple transparently. Use -Sm to plot the Global CMT seismic moment tensor with zero trace. Use -Sd to plot only the double couple part of moment tensor. Use -Sz to plot the anisotropic part of moment tensor (zero trace). 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. Append +u to have the text appear below the beach ball (default is above). 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 beach ball. Entries in these columns are necessary with the -C option. 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 above or below the beach ball (optional).



-Spscale[+ffont][+jjustify][+odx[/dy]]

Focal mechanisms given with partial data on both planes. 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 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. Append +u to have the text appear below the beach ball (default is above). 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 beach ball. Entries in these columns are necessary with the -C option. 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 above or below the beach ball (optional).



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

Principal axis. 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 (that is seismic scalar moment = 4*10e+23 dynes-cm) in inch (unless c, i, or p is appended). (-T0 option overlays best double couple transparently.) Use -Sx to plot standard Global CMT. Use -Sy to plot only the double couple part of moment tensor. Use -St to plot zero trace moment tensor. 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. Append +u to have the text appear below the beach ball (default is above). 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 beach ball. Entries in these columns are necessary with the -C option. 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 above or below the beach ball (optional).



OPTIONAL ARGUMENTS

Set map boundary frame and axes attributes.

Offsets focal mechanisms to the longitude, latitude specified in the last two columns of the input file before the (optional) text string. A small circle is plotted at the initial location and a line connects the beachball to the circle. Specify pen and optionally append +spointsize to change the line style and/or size of the circle. [Defaults: pen as given by -W; pointsize is 0].

Plots events between depmin and depmax.

Selects filling of extensive quadrants. Usually white. Set the color [Default is white].

Sets one or more attributes; repeatable. The various combinations are
Computes and plots 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]
Sets the color or fill pattern for the T axis symbol. [Default as set by -E]
Sets the color or fill pattern for the P axis symbol. [Default as set by -G]
Use the psvelomeca input format without depth in the third column.
Draws the P axis outline using default pen (see -W), or sets pen attributes.
Draw a box behind the label (if any). [Default fill is white]
Draws the T axis outline using default pen (see -W), or sets pen attributes.
Overlay zero trace moment tensor using default pen (see -W), or sets pen attributes.

Selects filling of focal mechanisms. By convention, the compressional quadrants of the focal mechanism beach balls are shaded. Set the color [Default is black].

Draws the "beach ball" outline with pen attributes instead of with the default pen set by -W.

Use the same size for any magnitude. Size is given with -S.

Does not skip symbols that fall outside frame boundary specified by -R [Default plots symbols inside frame only].

Plots 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].


Draw GMT time stamp logo on plot.

Select verbosity level [c].

Set pen attributes for all lines and the outline of symbols [Defaults: width = default, color = black, style = solid]. This setting applies to -C, -L, -T, -Fp, -Ft, and -Fz, unless overruled by options to those arguments.

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

Shift plot origin.

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

Replace input columns that equal nodata with NaN.

Only accept data records that match the given pattern.

Skip or produce header record(s).

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

Select perspective view.

Set transparency level in percent.

-:[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 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 exits.
-? or no arguments
Print a complete usage (help) message, including the explanation of all options, then exits.
Temporarily override a GMT default setting; repeatable. See /gmt.conf for parameters.

EXAMPLES

The following file should give a normal-faulting CMT mechanism:

gmt meca -R239/240/34/35.2 -Jm4c -Sc2c -h1 -pdf test << END
#lon lat depth str dip slip st dip slip mant exp plon plat
239.384 34.556 12. 180 18 -88 0 72 -90 5.5 0 0 0
END




REFERENCES

Bomford, G., Geodesy, 4th ed., Oxford University Press, 1980.

Aki, K. and P. Richards, Quantitative Seismology, Freeman, 1980.

F. A. Dahlen and Jeroen Tromp, Theoretical Global Seismology, Princeton, 1998, p.167. Definition of scalar moment.

Cliff Frohlich, Cliff's Nodes Concerning Plotting Nodal Lines for P, Sh and Sv, Seismological Research Letters, Volume 67, Number 1, January-February, 1996

Thorne Lay, Terry C. Wallace, Modern Global Seismology, Academic Press, 1995, p.384.

W.H. Press, S.A. Teukolsky, W.T. Vetterling, B.P. Flannery, Numerical Recipes in C, Cambridge University press (routine jacobi)

AUTHOR

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

SEE ALSO

polar, coupe, gmt, basemap, plot

COPYRIGHT

2019, The GMT Team

September 7, 2019 6.0.0rc4