Module BP 11 - dynamicearth.de

11Subduktion zonen
R. Bousquet 2009-2010
Module BP 11 - 11
Earthquakes
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Module BP 11 - 11
Haiti Earthquake 12.01.2010
USGS
R. Bousquet 2009-2010
Module BP 11 - 11
Haiti Earthquake 12.01.2010
USGS
R. Bousquet 2009-2010
Module BP 11 - 11
Haiti Earthquake 12.01.2010
USGS
http://earthquake.usgs.gov/
R. Bousquet 2009-2010
Module BP 11 - 11
Haiti Earthquake 12.01.2010
USGS
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Module BP 11 - 11
Haiti Earthquake 12.01.2010
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Module BP 11 - 11
Haiti Earthquake 12.01.2010
Calais, RENASS
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Haiti Earthquake 12.01.2010
RENASS
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Haiti Earthquake 12.01.2010
Woods Hole
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Haiti Earthquake 12.01.2010
USGS
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Back-arc basin
Spreading axis
Magmatic arc
Magmatic
front
Forearc
Forearc
basin
Trench
Accretionary
prism
Outer
trench
high
0
Depth (km)
Arc crust
500 C
1
Lithospheric
mantle
50
Convecting 2
Asthenosphere
S
tin
c
u
d
ub
he re
p
s
o
g lith
500 C
1000 C
Oceanic crust
Asthenosphere
motions
Plate motions
100
Partial melt diapir
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2
Areas of melt
generation
Fluid pathways
150
400
300
200
100
Distance from trench (km)
0
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Module BP 11 - 11
An accretionary wedge is a wide submarine mountain belt…
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Makran wedge
500 Km !
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Marianna wedge
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Lesser Antilles wedge
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Barbados accretionary prism
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from Kopp
17
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Sunda wedge
from Kopp and Kukowski
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Nankai wedge (Japan)
P. Henry & JOIDES Team
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Cascadia wedge
Gutscher et al., 1996
31
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Ionian Sea wedge
N. Kukowski et al. / Marine Geology 186 (2002) 29^42
Fig. 1. Bathymetric map of the Ionian Sea region, showing the tectonic setting of the IMERSE experiment with the location of
the seismic pro¢les across the WMR. The part of line 5 shown in Fig. 2 is marked in bold, CS refers to Cyrene Seamount.
Kukowski et al., 2002
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Ionian Sea wedge
Fig. 2. Interpretation of a seismic section (in time) through the Mediterranean Ridge accretionary wedge based on the results of the IMERSE project and in particular pro¢le 5A (Reston et al., 1999a). See text for details of the tectonic interpretation.
Kukowski et al., 2002
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Ionian Sea wedge
N. Kukowski et al. / Marine Geology 186 (2002) 29^42
Kukowski et al., 2002
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Types of accretionary wedge
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Mechanisms of accretion
NW
Cascadia wedge
SE
Gutscher, M.A., Kukowski, N.,
Malavieille, J., and Lallemand, S., 1998, JGR
Changes in detachment levels
Entrained duplexes
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Kukowski, Lallemand, Malavieille,
Gutscher & Reston, 2002, Marine Geology
Underplating +
Frontal accretion
- Strain partitioning
- Two different growth processes acting simultaneously
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Mechanisms of accretion
In the eighties, mechanical modeling of mountain building bring geologists
to consider mountain belts as
crustal scale accretionary wedges.
Taiwan wedge model by Davis, Suppe & Dahlen, 1983
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-> Coulomb wedge theory
(The wedge is considered to deform homogeneously).
* Different tectonic regimes depending on wedge stability : critical,
subcritical, supercritical…
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Critical taper
do not give any information on how the interior of the wedge deforms
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Modeling accretionary wedge
Sediments
Fixed plate (Backstop)
S
Mobile
plate
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Malavieille, com. pers.
Module BP 11 - 11
Modeling accretionary wedge
Sediments
Fixed plate (Backstop)
S
Mobile
plate
Malavieille, com. pers.
Fixed Backstop
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Coloured sand layers
traction
S
“the sandbox“
Plastic sheet
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Modeling accretionary wedge
High friction
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Low friction
Malavieille, com. pers.
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Modeling accretionary wedge
High friction
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Low friction
Malavieille, com. pers.
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Modeling accretionary wedge
High angle
underthrusting
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Low angle
Frontal accretion
Biagi & Malavieille, 1987
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Modeling accretionary wedge
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Localized exhumation window
Progressive exhumation
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Impact of backstop geometry
Malavieille & Biaggi., 1987
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Types of wedge & exhumation of HP rocks
Extension: Crete
Croos-­cutting sets
of normal faults
frontal accretion
Major narmal fault
(detachment)
0
Blueschist
Platt, 1986
Depth (km)
20
40
underplatting
by imbrication & folding
Underplating & erosion : South-­Chile, Taiwan
Small normal faults
erosion
frontal accretion
0
20
Ring & Brandon, 1994
Depth (km)
amincissement
ductile
40
underplating
Blueschist, Eclogites
0
20
Cloos, 1982
40
matter flow
LP rocks
”jNEDU
HP rocks
•jNEDU
after Bousquet, 1998
0
100 km
Depth (km)
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"Corner flow" or subduction channel : Western Alps
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Tectonic plates around Taiwan
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TAIWAN
Image K-J Chang
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Geodynamic
setting
Taiwan,
The classical example
of
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Arc-continent collision !
Why not?
But, what does it mean?
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Tomography below Taiwan
North profile
Lallemand et al., 2001
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Tomography below Taiwan
Profile in the
Middle of the
island
Lallemand et al., 2001
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Tomography below Taiwan
South profile
Lallemand et al., 2001
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> 8cm/yr
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Seismicity around Taiwan
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Seismicity around Taiwan
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Seismicity around Taiwan
Carena et al., 2002
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Taiwan’s wedge geometry
Orogenic wedge
Backstop
S
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Subducted plate
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Taiwan’s wedge geometry
Orogenic wedge
Backstop
S
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Subducted plate
Carena et al., 2002
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3D geometry
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Lallemand et al., 2001
Oblique subduction
of the chinese continental margin
under the Philippine plate
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Taiwan: geodynamic evolution
Lallemand et al., 2001
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Taiwan: geodynamic evolution
Lallemand et al., 2001
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Module BP 11 - 11
Taiwan: geodynamic evolution
Lallemand et al., 2001
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Taiwan: geodynamic evolution
Lallemand et al., 2001
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Taiwan: geodynamic evolution
Lallemand et al., 2001
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Taiwan: geodynamic evolution
Lallemand et al., 2001
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Taiwan: analogical models
Malavieille, com. pers.
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Taiwan: analogical models
Although convergence & erosion being uniform, deformation recorded in
the wedge is complex
Malavieille, com. pers.
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Taiwan: structure vs model
Malavieille, com. pers.
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Metamorphic evolution & erosion distribution
Willett et al. 2001
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Lallemand et al., 1999
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Main forces of plate tectonics
plate draged by convection
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plate pushed by density changes
of the oceanic plate
plate pulled by downgoing slab
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Slab dip vs. age
Lallemand et al., 2005
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Back-arc dynamics
Non oceanic back-­arc
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Back-­arc oceanic crust
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Back-arc dynamics
Major Pacific slab geometries classified by groups of deep slab dips except
the first group, which concerns flat subductions with variable deep slab
dips: 30° to 50°, 50° to 60°, 60° to 70°, steeper than 70°. Active arc/ back-arc
compression is observed for slab dips lower than 50°, whereas active arc/
back-arc extension occurs only for slabs dips steeper than 50°.
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Absolute vs effective trench migration
The shape produced by sinking slab elements depends upon the speed of
the trench relative to the underlying mantle
Similar profiles may result from
(a) a fast trench and quiescent mantle or
(b) a stationary trench and a fast
flowing upper mantle; in both cases the
effective migration rate is the same.
Even in the absence of the global mantle
flow, this coupling will result in steeper
dips than produced in a.
(c) Conversely, a fast moving trench
may have zero effective velocity.
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(d) Plate motions alter mantle flow
fields unless completely decoupled.
(e) In one-sided subduction, plate/
mantle coupling will generate a flow
associated with the trench's motion,
thus limiting changes in effective
migration.
Tao & O’Connell, 1992
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Relative motions of subduction zones
Arcay et al., 2008
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Relative motions of subduction zones
Arcay et al., 2008
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Plate tectonic forces
Vup
Friction
Arc deformation
Trench
1
3c
3a Bending
Ridgeïpush
Interplate decoupling depth, zdec
Vs
Slabïpull
Mantle shear
2
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2
Vsub
3b Intraslab deformation
Basal mantle shear