Announcements Mihai's lectures are available on web Field trip during lab this week Posta-Quemada...
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Transcript of Announcements Mihai's lectures are available on web Field trip during lab this week Posta-Quemada...
Announcements
Mihai's lectures are available on web
Field trip during lab this week
Posta-Quemada fold exercise- due Wed in lecture
Nov. 13: Draft of fault paper due in lecture!
Strike-slip fault systems(D&R: 357-371)
1. Tectonic settings and significance
2. Geometries
3. Active strike-slip faults- EQs!
4. mineralization + petroleum
At the scale of plate tectonics, transform (strike-slip) plate boundaries are subordinate to convergent and divergent plate margins- but they play a critical role
oceanic (ridge-ridge) transform faults, revisited
Continental strike-slip faults- the San Andreas
The Alpine fault in New Zealand transfers slip
between two subduction zones (trench-trench
transform)
What is the sense of slip?
Major active continental strike-slip faults in Asia
tectonic extrusion or escape hypothesis
Strike-slip faults can transfer slip between different thrust or extensional systems
Strain can be partitioned into different styles of fault systems- analyze with vector diagrams
Strain partitioning in oblique convergent margin settings
Fault traces are rarely straight- they can curve, branch, or be arranged en echelon.
This leads to a wide variety of strike-slip related deformation
Transtension in releasing bends may lead to development of sag ponds and pull-apart basins
Restraining bends and transpressional deformation- folds and thrusts
The San Andreas bend near Los Angeles:thrusting related to strike-slip faulting
Many strike-slip fault systems are characterized by faults that converge downward and form flower structures
compressional setting: "positive" or "palm tree" flower structure
extensional setting: "negative" or "tulip" flower structure
Some flower structures look like duplexes turned on their side- strike-slip duplexes
Riedel shears, revisited- especially common in strike-slip fault systems
R: synthetic Riedel shearR': antithetic Riedel shearP: synthetic shear, subordinate to R and R' or absent
Altyn Tagh fault, China
summary ofstrike-slip-relateddeformation
What is important about strike-slip faults and why do we care?
1. Many active strike-slip faults are associated with high slip rates, major earthquakes, and lithospheric plate boundaries
Big faults yield big quakes + lots of people = trouble!
e.g., San Andreas fault, Anatolian fault in Turkey, strike-slip faults in Asia
Significance of strike-slip fault systems for oil
Many Archean and Phanerozoic mineral deposits (especially gold) are associated with zones of strike-slip deformation
镜头指向:北东
镜头指向:南
镜头指向:南
斜列式地震裂缝。
镜头指向:东
近水平擦痕。镜头指向:南
平直裂缝。镜头指向:东
NEXT LECTURE:
Cleavages and passive folding(D&R pp. 424-456)
Important terminology/conceptsridge-ridge and trench-trench transform faults
concept of continental extrusion or escape
strike-slip faults as transfer faults
strain partitioning
oblique convergence
releasing vs. restraining bend
transpression vs. transtension
sag ponds and pull-apart basins
flower structures
strike-slip duplexes
right-stepping vs. left-stepping fault arrays
folds in strike-slip zones
Riedel shears