Subduction Zones of the World: Comparison to the Cascadia Subduction Zone and the Potential for Producing Large-scale Earthquakes By Alicia Thompson

Outline Subduction Zone and Large-scale earthquake Tour of subduction zones South American New Zealand Sumatra Nankai Kamchatka and Kurile Alaska and Aleutian Cascadia Conclusion

Subduction Zone What is a subduction zone? Ocean to Continental Ocean to Ocean www3.telus.net/.../images/subduction.gif

What can cause a large-scale earthquake?                                                                                         What can cause a large-scale earthquake?                                                                                         B. During an http://pubs.usgs.gov/circ/c1187/

Robert McCaffrey

Subduction rate (mm/yr) Age of the Plate (Ma) Date M Region Subduction rate (mm/yr) Age of the Plate (Ma) Date M South Chile 70 26 1960 9.6 New Zealand 43 120 1931 7.8 North Sumatra 33 72 2004 9.3 Nankai 57 20 1707 8.8 Kamchatka 78 84 1952 8.9 Kuriles 81 110 1963 8.5 Alaska 54 42 1964 West Aleutian 73 1965 8.7 Cascadia 9 1700 9.1 From Seth Stein and Emile A. Okal

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

New Zealand

New Zealand

The Indonesian Islands

Sumatra, 2005 Thrust-faulting on the interface of the India plate and the Burma plate Fault- rupture propagated to the northwest from the epicenter for about 500 km with a maximum displacement of the plane about 20 meters

Japanese islands

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 Kurile 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 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 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 Aleutian Alaska 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 Aleutian 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 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 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/image001.jpg

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

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.