Transcript Subduction Zones of the World: Comparison to the Cascadia

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?
B. During an
http://pubs.usgs.gov/circ/c1187/
Robert McCaffrey
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
9.3
West
Aleutian
73
84
1965
8.7
Cascadia
42
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 WadatiBenioff 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/image00
1.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
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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%2
0Hazards
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.