Seismo-tectonic maps

Visualizing a region's seismotectonics is a powerful way to quickly identify processes and questions.

My group uses the software tectoplot, in development by Kyle Bradley, to explore and communicate tectonic processes around the Earth. The resulting maps highlight the value of visualizing and integrating datasets. The maps are generated in tectoplot, and then modified slightly in Adobe Illustrator to improve the labelling and legend. Tectoplot allows any user to quickly leverage publically available datasets to generate stunning and illuminating maps.

Tectoplot is available from Kyle Bradley here: https://github.com/kyleedwardbradley/tectoplot. Note that since the code is still in development, in some cases the specific functions may have been modified since these maps were generated.

This map of summed seismic moment for shallow earthquakes (0-50 km depth) highlights how subduction zones are responsible for the largest generation of seismic energy. Southeast Asia is particular is surrounded by earthquake-generating faults.

Code: tectoplot -RJ W 130 -r g -t 10m -t0 -tt 50 -zcat ANSS ISC -zmag 4 10 -zdep 0 50 -znoplot -z -seissum 0.5 -o global_seis_0_50 -noframe

While the most famous earthquake in Taiwan in the 1999 Mw7.5 Chi-Chi earthquake, in the western foreland, northeastern Taiwan has experienced significant seismicity as well. A Mw6.4 earthquake in 2018 is one part of a large cluster of seismicity over the last decade.

Code: tectoplot -RJ UTM -r 121.3 122.2 23.8 24.8 -im easttaiwan_intensity.tif -clipon TW -t 01s -tsl -tx -clipoff -a -zcat ANSS ISC -z -zline 0 -zcrescale 2.5 -c -cw -o hualien -time 2010 2022 -pgs 0.2 -legend onmap -scale 20k 122 23.6

A Mw5.9 earthquake in the Walker Lane region, on the eastern border of the Sierra Nevada, highlights the complex oblique-normal tectonics of this region on the western edge of the Basin and Range, USA.

Code: tectoplot -RJ UTM -r -120 -118.5 37.4 39 -t 01s -t0 -tx -z -zline 0 -zcrescale 3 -c ORIGIN -zctime -eqlabel 5.5 yearmag -pgs 0.2 -legend onmap -cw

The Pyrenees formed in collision, but that ended long ago. This seismicity represents slow extension at <1 mm/yr.

Code: tectoplot -RJ UTM -r -3.5 4 41 44.5 -im colored_intensity.tif -clipon ES,FR,AD -t 03s -tmult -tsl -tx -clipoff -a -zcat ISC -z -zline 0 -zcrescale 3 -c ORIGIN -cw -o pyrenees -legend onmap -eqlabel 5 yearmag

(Note: colored_intensity.tif generated with previous command line and moved to main folder.)

Montana is east of typical "earthquake country", but has still experienced significant seismicity, including a Mw7.3 earthquake in 1959. Sporadic smaller events have been recorded across the central and eastern parts of the state.

Code: tectoplot -RJ UTM -r US.MT -clipon US.MT -t 15s -clipoff -z 1 20 -c ORIGIN -cw -zcrescale 3 -pg US.MT show -noframe -t0 -tx -tt 20 -scale 200k -106 44.5 -eqlabel 6 yearmag -title Seismicity in Montana -legend onmap -o montana

Nevada hosted the 4th largest earthquake in the contiguous USA in the last century: the 1954 Mw7.2 Fairview Peaks earthquake, which generated 7 m scarps. This event was preceded by two large foreshocks in the 6 months before the event, and is a manifestation of the active extension in the Basin and Range.

Code: tectoplot -RJ UTM -r US.NV+R0.1 -clipon US.NV -t 03s -g NA -clipoff -pg US.NV show -zline 0 -zfill red -z 1 30 -zcrescale 4 -c ORIGIN -cw -noframe -t0 -tx -clipon US.NV -i 4 -setvars { GPS_FILLCOLOR black GPS_LINEWIDTH 0p } -clipoff -eqlabel 7 yearmag -legend onmap -o nevada -scale 100k A

Offshore western Mexico: the Rivera Plate broke off of the Cocos Plate ~10 million years ago. The spreading centers here are nearly silent - we see only strike-slip events at the transforms and thrust events showing northeastward subduction.

Code: tectoplot -RJ UTM -r -112 -100 15 25 -t -t0 -pe -z -c -cw -p MORVEL na -pf 200 -pa -o mexico -legend onmap -pgs 2

The 1992 Mw7.3 Landers earthquake triggered two other notable quakes: the 1992 Mw6.5 Big Bear, and the 1999 Mw7.1 Hector Mine. Given the lack of earthquakes on the San Andreas in the last 100 years, these are some of the most significant Californian earthquakes in living memory.

Code: tectoplot -RJ UTM -r -117.4 -115.8 33.6 35.2 -t 01s -t0 -tx -tpct -30 99 -af -z -c ORIGIN -zcrescale 2 -o landers -zctime -eqlabel 6.5 datemag -pgs 0.2 -legend onmap -zline 0 -cw -pgs 0.5

Coloring seismicity by time lets the aftershocks of the Ridgecrest sequence stand out, and illustrates how the event stopped abruptly at the Garlock fault. Also visible: the orthogonal faults activated in the sequence - although here, the map is not projected, resulting in angle distortions; a UTM projection would remedy this (-RJ UTM).

Code: tectoplot -r -118.1 -116.8 34.8 36.3 -t 01s -t0 -tx -tpct -30 99 -af -z -c -zcrescale 2 -o ridgecresttime -zctime -eqlabel 6 datemag -pgs 0.2 -legend onmap -zline 0 -cw

Twin Mw6.0 earthquake ruptured the Chilean megathrust on July 4, 2021 , just north of aftershock region of the 2015 Mw8.3 Illapel earthquake.

Code: tectoplot -RJ UTM -r -75 -68 -34 -27 -t 03s -t0 -tt 30 -a -z 1 50 -zsort depth up -c -cw -eqlabel 8 yearmag -o chile20152016 -pgs 2 -legend onmap -time 2015 2017 -title Seismicity 2015-2016

Shallow seismicity (0-30 km) in Japan highlights not just the astonishingly wide updip active region of the Japan Trench, but also an intricate network of faults cutting across and through the country. Seismicity catalog is ISC.

Code: tectoplot -RJ UTM -r 128 146 30 46 -t -t0 -tx -a -ac darkgreen@80 blue@80 -zcat ISC -z -zsort depth up -o japanshallow -zdep 0 30

In the Afar Triangle, seismicity and GPS data illustrate how the plate boundary in the Red Sea jumps to the west as it approached the triple junction.

Code: tectoplot -RJ F 41.5 12 7 -t 15s -t0 -tt 30 -tpct 1 99 -vc black 0.2p 0.05i -zcat ISC ANSS -z -zline 0 -c -cw -o afar -legend onmap -g AF -i 4 -setvars { GPS_FILLCOLOR black GPS_LINEWIDTH 0p }

Code:
tectoplot -RJ F 88 33 15 -title Thrust -t -t0 -tx -af 0.5 black -ct t -c -cw -zcrescale 2 -pss 8 -keepopenps

tectoplot -RJ F 88 33 15 -title Strike-slip -t -t0 -tx -af 0.5 black -ct s -c -cw -zcrescale 2 -pss 8 -keepopenps -pos 9i 0i -ips ./tempfiles_to_delete/map.ps

tectoplot -RJ F 88 33 15 -title Normal -t -t0 -tx -af 0.5 black -ct n -c -cw -zcrescale 2 -pss 8 -keepopenps -pos -9i -9.5i -ips ./tempfiles_to_delete/map.ps

tectoplot -RJ F 88 33 15 -title Seismicity, GPS relative to Europe -t -t0 -tx -af 0.5 black -zcat ISC -z 1 50 -zline 0 -zsort depth up -g EU -setvars { GPS_FILLCOLOR black GPS_LINEWIDTH 0p } -pss 8 -pos 9i 0i -ips ./tempfiles_to_delete/map.ps

The Tibetan Plateau contains all three kinds of earthquakes:
(1) Thrusts on the borders, in the Himalaya, Tien Shan, Qilian Shan, and Longmen Shan.
(2) Strike-slip accommodating squeezing of the plateau out to the east and southeast.
(3) Normal faulting in the interior, allowing east-west gravitational collapse.

Volcanoes in east Java stand out as stunning geomorphological features.

Code: tectoplot -r 112.2 114.5 -8.3 -7.5 -t 01s -t0 -pgs 0.5

The Sumatran Fault cuts right across the topographic bulge produced by Toba Supervolcano in Sumatra.

Code: tectoplot -RJ UTM -r 98 99.5 1.8 3.2 -t 01s -t0 -o toba

The North and East Anatolian Faults are strike-slip, but a moderate earthquake just west of their intersection exhibited more oblique behavior on June 25, 2021.

tectoplot -RJ UTM -r 38 42 38 40 -t 03s -t0 -zcat ISC ANSS -af 0.5 black -z -c -o turkey -zline 0 -eqlabel 6.7 yearmag -pgs 1 -legend onmap -author

Seismicity outlines the active faults in the Bay Area, California.

Code: tectoplot -RJ UTM -r -122.8 -120.7 36 38.3 -t 03s -tr -t0 -z -c -zcrescale 3 -pgs 0.5 -zline 0

Seismicity in Greece is incredibly complex - and like in many parts of the world, many of the known large earthquakes occurred >60 years ago.

Code: tectoplot -r 26 29 34 38 -t 03s -t0 -zcat ISC -z 1 50 -c -pgs 1 -o greece_eq4 -eqlabel 6 datemag -zline 0 -zcrescale 2 -legend onmap

Maps of seismicity can outline geographic features. Here, the map illustrates the subduction of the Ionian slab, the location of the Appenines, and the loop around into the Alps, as well as the vast swath of seismicity across Greece.

tectoplot -RJ UTM -r IT,GR+R1 -zcat ISC -z -legend onmap -c

California, as seen through the lens of earthquakes.

Code: tectoplot -r US.CA -z -zline 0 -o cali

Macroscopic axial planar cleavage in northern Myanmar.

Code: tectoplot -r 95.85 96.15 25.45 25.7 -t 01s -t0 -o axialplanar -scale 10k 96.05 25.47 -pgs 0.1

Subduction zone seismicity is often best visualized in cross section. Here, the seismicity of northern New Zealand illustrates the Pacific Plate diving to the northwest.

The cross section shows a fairly clean plate in the upper 100 km, widening to a broad zone between 100-300 km.

Code: tectoplot -r 171 180 -43 -35 -t 15s -t0 -zcat ISC ANSS -z -c -title Seismicity of northern New Zealand -RJ UTM -o nz -sprof 174 -36 179 -40 100k 0.5k -oto -profdepth -400 5 -showprof 1 2 -legend onmap

New Zealand hosts two oppositely vergent subduction zones - but the seismicity profiles are very different: a wide zone of deep seismicity in the north, and a tight a more limited clustering in the south.

Code: tectoplot -r 166 179 -48 -34 -t 15s -t0 -zcat ISC -z -c -title Seismicity of New Zealand -RJ UTM -legend onmap -o nz

The Bangladesh fold-and-thrust belt is the shallowest manifestation of the subduction of the Indian plate beneath Myanmar.

Code: tectoplot -r 91 93.6 21 25 -t 01s -t0 -pgs 1 -o bangladesh

Page updated

Google Sites

Report abuse