Lecture 6: Transforms faults and Convergent margins

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Lecture 6 Transforms faults and Convergent
margins
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Kane FZ
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South Atlantic Spreading Rate
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EPR 9 North
Compression
Cocos plate
Pacific plate
Extension
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Gravity
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Bain FZ Multiple new FZs under extension FZs
re-combine under compression
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Udintsev FZ, Pac-Ant Ridge
Note Transverse ridges
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Also know as J structures
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Pitman FZ, Pac-Ant Ridge
Note J structures and Transverse ridges
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Hawaii classic flexural bulge due to load of
seamounts
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Satellite gravity
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Kuril Trench classic example of flexure at a
trench
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Flexure cause by differential subsidence
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Gravity anomalies due to flexure across fracture
zones
Menard FZ
Udintsev FZ
Eltanin FZ
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Convergent Margins
Focal Depths green lt 50 km, yellow 50 to 250
km, red gt 250 km
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KKV Fig 9.1
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ocean - ocean
MT
ocean - continent
KKV Fig 9.18
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Focal Depths green lt 50 km, yellow 50 to 250
km, red gt 250 km
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Focal Depths Green 0 50 km Yellow
50 250 km Red gt 250 km
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Ontong Java Plateau
Note Collision of Ontong Java Plateau
with trench around 15 Ma led to reversal of
subduction polarity in SW Pacific
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For EQ of size small w.r.t wavelength
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For earthquakes at plate boundaries
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Note these are cross sections of beach balls
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Double Benioff Zone
KKV Fig 9.12
Upper plane metamorphic reactions in subducted
crust Lower plane metamorphic reactions in
subducted mantle
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Ontong Java Plateau
Tonga Trench