Subduction Zones of the World: Subduction Zones of the World: Comparison to the Cascadia Comparison to the Cascadia

Subduction Zone and the Subduction Zone and the Potential for Producing Large-Potential for Producing Large-

scale Earthquakesscale Earthquakes

By Alicia ThompsonBy Alicia Thompson

OutlineOutline Subduction Zone and Large-scale earthquake Subduction Zone and Large-scale earthquake Tour of subduction zonesTour of subduction zones

– South American South American – New ZealandNew Zealand– Sumatra Sumatra – Nankai Nankai – Kamchatka and KurileKamchatka and Kurile– Alaska and AleutianAlaska and Aleutian– Cascadia Cascadia

Conclusion Conclusion

Subduction Zone

What is a What is a subduction zone?subduction zone?

Ocean to Ocean to Continental Continental

Ocean to OceanOcean to Oceanwww3.telus.net/.../images/subduction.gifwww3.telus.net/.../images/subduction.gif

What can cause a large-scale What can cause a large-scale earthquake?earthquake?

                                                  

                                     

                                                     

                                   B. During an

http://pubs.usgs.gov/circ/c1187/

Robert McCaffrey

RegionRegion Subduction rate Subduction rate (mm/yr)(mm/yr)

Age of the Plate Age of the Plate (Ma)(Ma)

Date Date MM

South South ChileChile

7070 2626 19601960 9.69.6

New New ZealandZealand

4343 120120 19311931 7.87.8

North North SumatraSumatra

3333 7272 20042004 9.39.3

NankaiNankai 5757 2020 17071707 8.88.8

KamchatkKamchatkaa

7878 8484 19521952 8.98.9

Kuriles Kuriles 8181 110110 19631963 8.58.5

AlaskaAlaska 5454 4242 19641964 9.39.3

West West Aleutian Aleutian

7373 8484 19651965 8.78.7

CascadiaCascadia 4242 99 17001700 9.19.1From Seth Stein and Emile A. Okal

South AmericanSouth American

During the 1960 During the 1960 Chile earthquake, the Chile earthquake, the western margin of western margin of the South American the South American Plate lurched as Plate lurched as much as 60 feet much as 60 feet relative to the relative to the subducting Nazca subducting Nazca Plate, in an area 600 Plate, in an area 600 miles long and more miles long and more than 100 miles wide. than 100 miles wide.

New ZealandNew Zealand

New ZealandNew Zealand

The Indonesian Islands The Indonesian Islands

Sumatra, 2005Sumatra, 2005

Thrust-faulting on the Thrust-faulting on the interface of the India interface of the India plate and the Burma plate and the Burma plate plate

Fault- rupture Fault- rupture propagated to the propagated to the northwest from the northwest from the epicenter for about epicenter for about 500 km with a 500 km with a maximum maximum displacement of the displacement of the plane about 20 meters plane about 20 meters

Japanese islands Japanese islands

Nankai Nankai

Location map of Nankai margin, illustrating the coseismic slip areas of the 1944 (light red filled contours) and 1946 (blue arrows denote rupture sequence) earthquakes obtained from the tsunami data and seismic wave data. Red contours indicate the plate depth from the sea floor. Areas marked in black represent locations with 2.5 km water depth and 7 km sub-bottom depth to the plate interface

Kamchatka and KurileKamchatka and Kurile

Kamchatka: Kamchatka: The rupture started in the north and propagated southwest for 600–700 km with a velocity of 3–3.5 km/s

The slip may represent two asperities, both in the down-dip portion of the ruptured fault: a smaller asperity near the initiation of the rupture and another, larger one, within the second half of the rupture.

Kamchatka and KurileKamchatka and Kurile

Kurile: Kurile: The rupture started in the south and propagated mainly to the northeast.

The latest significant event in the Kuriles (M8.3) occurred on November 15, 2006 in the central arc. Prior to this event, the 250-km-long segment of the arc between the 1918 rupture in the southwest and the 1915 rupture in the northeast has been recognized as a seismic gap

Kamchatka and KurileKamchatka and Kurile The consequence of this is that the subducting

lithosphere is relatively cold and thick and the Wadati-Benioff zone is clearly defined by hypocenters plunging to depths of 600 km south of the southern tip of Kamchatka.

There is a gap in seismicity that occurs between 200–300 km within the Kamchatka slab. This is a common observation in deep slabs around the world.

Later, deeper earthquakes increase in numbers due to transformational faulting related to phase transitions in the deep part of the upper mantle. In Kamchatka, resumption of seismic activity starts at 400–500 km.

Alaska and AleutianAlaska and Aleutian

Alaska 1964: AAlaska 1964: A unilateral rupture started in the Prince William Sound region and propagated southwest for ~800 km.

The studies indicate two major moment release areas. The larger asperity was located near the epicenter, and a second, smaller one was within the second half of the rupture zone near Kodiak Island.

Alaska and AleutianAlaska and Aleutian

Aleutian: A Aleutian: A unilateral rupture propagating from southeast to northwest for about 600 km.

Three major pulses of moment release were identified from the analysis of teleseismic P‑waves which correlate with Rat, Buldir, and Near tectonic blocks

Alaska and AleutianAlaska and Aleutian

The maximum depth of seismicity changes from 250 km to 50 km from east to west.

the slab seismicity below 100 km is characterized by dips that vary smoothly from shallow (45°) in the eastern Aleutians to steep (60°) in the central Aleutians and slightly shallower and less well resolved dip (~50°) in the far western Aleutian.

Cascadian Subduction ZoneCascadian Subduction Zone

Juan de Fuca plate subducts from about 2°–7° to 12° at a shallow depth of about 60–70 km

www.bhrc.ac.ir/.../subduction_files/www.bhrc.ac.ir/.../subduction_files/image001.jpg image001.jpg

Conclusion Conclusion

By understanding how mega-thrust mega-thrust earthquakes occur in earthquakes occur in other subduction zones subduction zones may be able to make preparations for potential preparations for potential earthquakes along the Cascadia earthquakes along the Cascadia Subduction zone.Subduction zone.

References References Long-Term Perspectives on Giant Earthquakes and Tsunamis at Subduction Zones by Kenji Satake1

and Brian F. Atwater2 Global frequency of magnitude 9 earthquakes by Robert McCaffrey NanTroSEIZE: The Nankai Trough Seismogenic Zone Experiment A Proposed IODP Complex Drilling

Project Revised October 1, 2003 Ultralong Period Seismic Study of the December 2004 Indian Ocean Earthquake and Implications for

Regional Tectonics and the Subduction Process by Seth Stein and Emile A. Okal The Great Sumatra Quake by Mark Wheeler Subduction zone coupling and tectonic block rotations in the North Island, New Zealand Laura M.

Wallace and John Beavan. Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand Appendix L: Cascadia Subduction Zone By Arthur D. Frankel1 and Mark D. Petersen1 www3.telus.net/.../images/subduction.gif Surviving a Tsunami—Lessons from Chile, Hawaii, and Japan Compiled by Brian F. Atwater, Marco

Cisternas V.1, Joanne Bourgeois2, Walter C. Dudley3, James W. Hendley II, and Peter H.Stauffer 1999; Reprinted 2001; revised and reprinted 2005 http://pubs.usgs.gov/circ/c1187/

USGS/Cascades Volcano Observatory, Vancouver, Washington http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/Maps/map_south_america_plates.html

Chapter 2 www.cdemhawkesbay.govt.nz/PicsHotel/cdem/Brochure/Facing%20the%20Risks_Chap%202_Earthquake%20Hazards

Subduction zone coupling and tectonic block rotations in the North Island, New Zealand Laura M. Wallace and John Beavan Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand

http://www.freewebs.com/mdreyes3/plate-tectonics.jpg Tectonic Summary Magnitude 9.1 OFF THE WEST COAST OF NORTHERN SUMATRA

Sunday, December 26, 2004 at 00:58:53 UTC http://neic.usgs.gov/neis/eq_depot/2004/eq_041226/neic_slav_ts.html

A new view into the Cascadia subduction zone and volcanic arc: Implications for earthquake hazards along the Washington margin Tom Parsons et others.