(13) Animating time-series (seismograms)

Here we demonstrate how one can animate a time-series so that the line grows in length and the pen thickness and color/intensity changes as it is being written. The trick we use is to convert the line into a series of densely-spaced points, using the dpi of the desired movie to determine the point resolution. These points are then animated like other points. We use events to preprocess the three components of a seismogram from a 2020 earthquake in the Aleutians and then animate it using real time. The three components evolve over time in each subplot panel while the rest of the presentation includes a source map and some metadata, plus a timer and progress indicator.

#!/usr/bin/env bash
# Movie of seismic waveforms from 2020-10-06 Alaska earthquake
# Epicenter 54.851N 159.851W
# Depth 31.0 km
# UTC time 2020-10-06 05:54:50
# Recorded at station Dolgoi Island, Mount Dutton, Alaska
# USGS event page: https://earthquake.usgs.gov/earthquakes/eventpage/us6000c5zm/executive
# DEM:  @earth_relief_06m
# Data: @waveform_AV.DOL.txt
# The data file @waveform_AV.DOL.txt contains 4 columns:
# UTC times, and three-component movement in east-west, north-south and up-down directions
# The finished movie is available in our YouTube channel as well:
# https://youtu.be/eq_-2nYYf-s
# The 66-sec, 1561 frame movie took ~15 minutes to render on a 24-core MacPro 2013.

# 0. Create an include file with key parameters
cat << 'EOF' > inc.sh
# 1. Create a dense point-file from the waveform data
cat << 'EOF' > pre.sh
gmt begin
	# 1a. Create dense point-files from the waveform data components so we can animate the lines
	gmt events @waveform_AV.DOL.txt -R${PLOT_DOMAIN} -JX20cT/3.5c -Ar${DPI} -i0,1+s1e-6,0 -f2T --GMT_INTERPOLANT=${SPLINE} > E.txt
	gmt events @waveform_AV.DOL.txt -R${PLOT_DOMAIN} -JX20cT/3.5c -Ar${DPI} -i0,2+s1e-6,0 -f2T --GMT_INTERPOLANT=${SPLINE} > N.txt
	gmt events @waveform_AV.DOL.txt -R${PLOT_DOMAIN} -JX20cT/3.5c -Ar${DPI} -i0,3+s1e-6,0 -f2T --GMT_INTERPOLANT=${SPLINE} > Z.txt
	# 1b. Setup the desired output times (24 frames per second)
	gmt math -T${TIME_RANGE}/24+i -o0 T --TIME_UNIT=s --FORMAT_CLOCK_OUT=hh:mm:ss.xxxxx = times.txt
	# 1c. Lay down the static part of the subplot
	gmt subplot begin 3x1 -Fs18.25c/3.5c -A -M0 -R${PLOT_DOMAIN} -X5.5c -Y0.75c
		gmt subplot set 0 -A"Z"
		gmt plot @waveform_AV.DOL.txt -Bpxafg -Bsxa1D -Bpyaf -BWsrt -W0.5p,darkgray -i0,3+s1e-6
		gmt subplot set 1 -A"N"
		gmt plot @waveform_AV.DOL.txt -Bpxafg -Bsxa1D -Bpyaf -BWsrt -W0.5p,darkgray -i0,2+s1e-6
		gmt subplot set 2 -A"E"
		gmt plot @waveform_AV.DOL.txt -Bpxafg -Bsxa1D -Bpyaf -BWSrt -W0.5p,darkgray -i0,1+s1e-6
	gmt subplot end
	# 1d. Create location map and metadata
	gmt text -R0/4.5/0/13 -Jx1c -F+j+f -B0 -X-5.25c -Y-0.5c <<- EOF
	2.25 12.5 CM 18p 2020-10-06
	2.25 11.7 CM 9p SE of Sand Point, Alaska
	2.25 11 CM 10p 54.851@.N, 159.851@.W
	2.25 10.5 CM 10p 31.0 km, Mw 5.9
	2.25 10.0 CM 10p 2020-10-06 05:54:50 UTC
	gmt grdimage -R190W/130W/30/75 @earth_relief_06m -Ba30+f -JM3.5c -I+d -Cterra --MAP_FRAME_TYPE=plain -X0.75c -Y0.5c -BWNbr --MAP_ANNOT_OBLIQUE=lat_parallel --FONT_ANNOT_PRIMARY=9p
	echo 161.86W 55.15N | gmt plot -St0.2c -GBlack
	echo 159.851W 54.851N | gmt plot -Sa0.25c -Gred -Wfaint
	gmt meca -Sc2.5c -M -G110/168/255 -W0.5p -Yh+0.5c <<- EOF
	-159.851 54.851 40.5 245 29 93 61 61 88 1.048 18
gmt end
# 2. Set up main movie script
cat << 'EOF' > main.sh
gmt begin
	gmt subplot begin 3x1 -Fs18.25c/3.5c -D -M0 -R${PLOT_DOMAIN} -X5.5c -Y0.75c
		gmt events Z.txt -Sc0.5p -Gred -Es+d0.5+r0.5 -Ms4+c1 -Mi0.5 -Mt+c0 -T${MOVIE_COL0} -c
		printf "%s -2.6\n%s 2.8\n" ${MOVIE_COL0} ${MOVIE_COL0} | gmt plot -W0.5p
		gmt events N.txt -Sc0.5p -Ggreen -Es+d0.5+r0.5 -Ms4+c1 -Mi0.5 -Mt+c0 -T${MOVIE_COL0} -c
		printf "%s -2.6\n%s 2.8\n" ${MOVIE_COL0} ${MOVIE_COL0} | gmt plot -W0.5p
		gmt events E.txt -Sc0.5p -Gblue -Es+d0.5+r0.5 -Ms4+c1 -Mi0.5 -Mt+c0 -T${MOVIE_COL0} -c
		printf "%s -2.6\n%s 2.8\n" ${MOVIE_COL0} ${MOVIE_COL0} | gmt plot -W0.5p
	gmt subplot end
gmt end
# 3. Run the movie
gmt movie main.sh -Iinc.sh -Sbpre.sh -CHD -Ttimes.txt -Nanim13 -Lc0+jTR+o0.25/0.25c -Ls"Station: Dolgoi Island, Mount Dutton, Alaska"+jTL+o5.5c/0.25c -H8 -Pb+w0.4c+jBR -Fmp4 -V -W -Zs -M500,png --FORMAT_DATE_MAP=-