(14) Animating earthquake focal mechanisms — GMT 6.5.0 documentation

# (14) Animating earthquake focal mechanisms

Here we make a movie of the focal mechanisms of large earthquakes from September 1981 to January 2018 in the flat subduction area in western Argentina and central Chile. The events are shown on a location map with a cross-sectional profile below. We use new capability in events to animate seismological symbols that are ultimately generated by meca and coupe. The data are obtained from the Global CMT web page at https://www.globalcmt.org/. Animation designed by Federico D. Esteban, University of Buenos Aires, Argentina.

    #!/usr/bin/env bash
    #
    # Movie of focal mechanisms from 09-1981 to 01-2018 in the flat subduction area
    # in western Argentina and central Chile. Shows a map with a profile.
    # Global CMT web page: https://www.globalcmt.org/
    #
    # DEM:  @earth_relief_03s
    # Data: @GCMT_1976-2017_meca.gmt
    #
    # The original data file jan76_dec17.ndk can be downloaded and rearranged to a gmt format with the followings commands:
    # URL="https://www.ldeo.columbia.edu/~gcmt/projects/CMT/catalog/jan76_dec17.ndk"
    # gmt which $URL -G
    # gawk '/^PDE/ {Date=$2; Time=$3; Lat=$4; Long=$5; Depth=$6; getline; Name=$1; getline; getline; Exp=$1; getline; mant=$11; strike1=$12; dip1=$13; rake1=$14; strike2=$15; dip2=$16; rake2=$17; print Long, Lat, Depth, strike1, dip1, rake1, strike2, dip2, rake2, mant, Exp, Date "T" Time, Name}' jan76_dec17.ndk | sed 's/\//-/g' > meca.gmt
    # gmt select meca.gmt -R-75.1/-63/-34.44/-30.35 > GCMT_1976-2017_meca.gmt
    # The GCMT_1976-2017_meca.gmt file is in the GMT Dataserver cache and can be accessed via @GCMT_1976-2017_meca.gmt
    # The finished movie is available in our YouTube channel as well:
    # https://youtu.be/Wk58r72g_nk
    # The 79-sec, 1896 frame movie took ~50 minutes to render on a 2017 iMac Pro.
    #
    # Author: ESTEBAN, Federico D.
    # Profile coordinates (in degrees) and perpendicular distance to filter the data and to show in the cross section.
    Long1=-75.02
    Long2=-63.65
    Lat1=-33.5
    Lat2=-31
    Dist=100k
    REGION=-75.1/-63/-34.44/-30.35	# Map Region
    # Angles (min/max/inc) for the profile inset
    Angles=15/60/15
    DEM=@earth_relief_03s
    # Other Variables
    W=22.73   			# Width Profile
    H=2.7c                   	# Profile Height
    PROJ=M23.78c			# Map projection and width
    X=0.115c			# Offset in X
    Y=0.91c				# Offset in Y
    # Create Profile
    cat << EOF > tmp_profile
    $Long1 $Lat1
    $Long2 $Lat2
    EOF
    # Filter Focal Mechanism. Create file with data Inside/Outside.
    gmt select @GCMT_1976-2017_meca.gmt -Ltmp_profile+d$Dist+p -fg > coupe_I.gmt
    gmt select @GCMT_1976-2017_meca.gmt -Ltmp_profile+d$Dist+p -fg > coupe_O.gmt -Il
    # Calculate variables (profile length, maximum depth of events (+10 to avoid clipping in the profile), vertical exaggeration, table of angles).
    KM=$(echo $Long1 $Lat1 | gmt mapproject -G$Long2/$Lat2+uk -o2)
    DepthMax=$(gmt info coupe_I.gmt -C -o5 | gmt math -Q STDIN 10 ADD =)
    VE=$(gmt math -Q $KM $H MUL $W DIV $DepthMax DIV = --FORMAT_FLOAT_OUT=%.2g)
    gmt math -T$Angles T SIND -o0,1,0 = | gmt math STDIN -T -C0 COSD = | gawk '$0=$0"@."' > angles.txt
    Ha=$(gmt math -Q $H 0.7c SUB =) # Height of inset with angles
    Wa=$(gmt math -Q $Ha $VE DIV =) # Width of inset with angles (calculated from vertical exaggeration to have same deformation as the profile)
    # 1. Create background plot and data files needed in the loop
    cat << EOF > pre.sh
    	gmt set FONT_LABEL 10p FONT_ANNOT_PRIMARY 7p MAP_FRAME_PEN thin,black MAP_GRID_PEN faint,gray
    gmt begin
    	# 1a. Create list of dates for the animation
    	gmt math -o0 -T1981-09-01T/2018-01-02T/7d T = times.txt
    	# 1b. Create cpt to paint the focal mechanism
    	gmt makecpt -T0/$DepthMax -Chot -I -H > q.cpt
    	# 1c. Draw profile
    	gmt basemap -R0/$KM/0/$DepthMax -JX$W/-$H -Bg25 -BwESn -Bxaf+l"Distance (km)" -Byaf+l"Depth (km)" -X$X -Y$Y
    	gmt inset begin -DjLB+w$Wa/$Ha+o0.1c/0.2c -F+p+gwhite+s+r -C0.15c
    		gmt plot angles.txt -Wthinnest,red -Bnw -Bg -R0/1/0/1 -JX?/-? --MAP_FRAME_TYPE=graph -Fr0/0 -i0-1+s0.9
    		gmt text angles.txt -F+f6 -N
    	gmt inset end
    	echo Vert. Ex. = $VE | gmt text -F+cBR+f9p -Gwhite -W1p
    	echo SW | gmt text -F+cTL+f12p -Gwhite -W1p
    	echo NE | gmt text -F+cTR+f12p -Gwhite -W1p
    	# 1d. Draw map
    	gmt grdimage $DEM -Coleron -I+nt1.2 -R$REGION -J$PROJ -Yh+0.3c
    	gmt coast -Df -N1/0.5p -Bf
    	gmt plot tmp_profile -W2p,red
    	gmt plot tmp_profile -Sc0.25c -Gred
    	gmt colorbar -Cq.cpt -DjBR+o1.75c/0.6c+w-6c/0.5c -Baf+l"Focal Depth (km)" -F+p+gwhite+s+r
    	gmt inset begin -DjTL+w3.5c+o-0.08c
    		gmt coast -Rg -JG-68.025/-32.01/? -Da -Gwhite -A5000 -Bg -W1/faint -Sdodgerblue2 -C- -N1
    		gmt basemap -R$REGION -J$PROJ -A | gmt plot -Wthin,darkred
    	gmt inset end
    gmt end
    EOF
    # 2. Set up main script
    cat << EOF > main.sh
    gmt begin
    	gmt set TIME_UNIT d
    	gmt events coupe_I.gmt -Wfaint -T\${MOVIE_COL0} -Es+r21+p42+d35+f1 -Mi0.6 -Ms1.5+c0.8 -Mt+c10 -R0/$KM/0/$DepthMax -JX$W/-$H -Y$Y -X$X -Z"coupe -Aa$Long1/$Lat1/$Long2/$Lat2+w$Dist -Q -Sc0.3c+f0" -Cq.cpt
    	gmt events coupe_O.gmt -Wfaint -T\${MOVIE_COL0} -Es+r21+p42+d35+f1 -Mi0.6 -Ms1.5+c0.8 -Mt+c10 -R$REGION -J$PROJ -Z"meca -Sc0.3c+f0" -Yh+0.3c
    	gmt events coupe_I.gmt -Wfaint -T\${MOVIE_COL0} -Es+r21+p42+d35+f1 -Mi0.6 -Ms1.5+c0.8 -Mt+c10 -R$REGION -J$PROJ -Z"meca -Sc0.3c+f0" -Cq.cpt
    gmt end
    EOF
    # 3. Run the movie
    gmt movie main.sh -Sbpre.sh -Chd -Ttimes.txt -Nanim14 -H2 -Fmp4 -D24 -Ml,png -Ve -Pd+ac0+jRM+w5.9c+o2.7/0.8c+P3,white+p1,red+a1+f11p,2,white \
    --FORMAT_CLOCK_MAP=- --FORMAT_DATE_MAP=dd-mm-yyyy --TIME_EPOCH=0000-01-01 -Zs
    rm coupe_*.gmt tmp_profile angles.txt