Brittle Deformation Flashcards
Classify the displacement field of fracture:
Opening or Extension
Mode I
Classify the displacement field of fracture: Sliding
Mode 2 (Shear Factures)
Classify the displacement field of fracture: Tearing - parallel to the edge slip
Mode 3 ( Shear Fractures)
Classify the displacement field of fracture: Closing especially as in Stylolites
Mode 4
Types of Joints: Have subparallel orientation and regular spacing
Systematic joints
types of Joints: have subparallel orientation and regular spacing
Systematic joints
types of joints: joints that does not share a common orientation and those with highly curved and irregular fracture surfaces
Nonsystematic joints
Joints that share a similar orientation in the same area
Joint set
Two or more joint set in the same area
joint system
joints that exhibit a feathered texture
Plumose joint
joints that are filled with minerals or aggregates
veins
joints that come in pair (unfilled or filled)
Conjugate joints
Differerentiate and draw the different termination along shear fractures
- wingcrack 2. horsetailing 3. splaying 4. Antithetic structures
Joint and Fracture Mechanism: indicates zones where the joint propagate rapidly
Hackle Marks
perpendicular to the direction of propagation and forms parallel to the advancing edge of the fracture
Arrest Lines
Engelder’s Joints: forms at depth with stress originate tectonically, and horizontal compaction occurs. Forms at depth less than 3km
Tectonic joints
Engelder’s joints: Forms at depth in response to abnormal fluid pressure arid involving hydrofracturing. Forms during burial and vertical compaction of sediment at depths greater than 5 km, where escaped of fluid hindered by low permeability, which creates locally abnormally high pressure
Hydarulic joints
Engelder’s joints: Forms when more than half of the original overburden has been removed from the rock mass
Unloading joints
Engelder’s joints: Form late in the history of an area and are ultimately oriented perpendicular to the original tectonic compressin that formed from the dominant fabric in the rock
Release joints
Non tectonic and Quasitectonic Fractures: Forms subparallel to surface topography, generally in massive rocks and corresponds to the unloading joint of engelder
Sheeting
Non tectonic and Quasitectonic Fractures: response to cooling and shrinkage of congealing magma
columnar joints
Non tectonic and Quasitectonic Fractures: Shrinkage due to evaporation of water in unconsolidated sediments
Mudcracks or Dessication Cracks
A fracture having an appreciable movement parallel to the plane of fracture
Faults
Anatomy of Faults: The actual movement surface
Faulit plane
Anatomy of Faults: the block resting on the fault plane
Hanging wall
Anatomy of the Faults: The block benath the fault plane
Foot wall
Anatomy of Faults: is the direction of the line formed by the intersection of a rock surface with a horizontal plane
Strike
Anatomy of Faults: The acute angle that a rock surface makes with a horizontal plane
Dip
Anatomy of faults: Down or up movement parallel to the dip direction of thefault
Dip-slip component
Anatomy of faults: movement parallel to the strike
Strike - slip component
Anatomy of faults: The combination of strike slip and dip slip
Oblique slip
Anatomy of faults: (True Displacements) the total amount of motion measured parallel to the direction of the motion
Net slip component
Anatomy of the Fault: Angle formed
rake
Anatomy of faults: the horizontal component of dip separation measured perpendicular to the strike of the fault
heave
Anatomy of faults: the vertical component measured in the vertical plane containing the dip
throw
Anatomy of faults: polished fault surface
slickensides
Anatomy of faults: aligned fibrous minerals on a movement surface
slickenfiber
Anatomy of faults: the amount of apparent offset of faulted surface such as bed or a dip measured in specified direction
Separation
Anderson classification of faults: dip slip fault in which the hanging wall has move down relative to the foot wall
Normal Fault
A block that moved down between to subparallel normal faults that dips toward one another
Graben
consist of two subparallel fault that dip towards each other so that the block in between remains high
Horst
A normal fault that exhhibits steep dip near the surface but flattened with depth. Concave up surface
Listric (Lag) Faults
branching characteristics of thrust and strike slip faults
splay
dip the same direction as the master fault and join the master fault to the depth
synthetic faults
Join the master fault at depth, but dip in the opposite directions
Antithetic fault
Folds associated to normal fault: a bend in rock strata that are otherwise uniformly dipping or horizontal
Monocline
Folds associated to normal fault: a normal fault may break and displace between rocks but die upward into the sedimentary cover
Drape fold
Folds associated to normal fault: form because of friction along the fault surface and occur along normal faults
Drag Folds
Folds associated to normal fault: Form along growth faults where the part of the downthrown block close to the fault is displaced the downward more than the parts further away
Reverse Drag folds and Rollover anticline
normal fault that is commonly form in a relatively unconsolidated sediments during deposition and produce thickened stratigraphic units in the downthrown block
Growth faults
30 degrees or less dip angle; hanging wall moves upward
Thrust Fault
45 degrees or more dip angle;
reverse fault
Thrust Faults: A high angle segment which may occur on all scales crossing units from few cm to a km or more thick
Ramp
Thrust faults: form by faulting the connecting limb of an anticline or syncline pair, overthrusting the HW anticline and preserving FW syncline
break thrust
Thrust faults: Formed independently by folding but not having a FW syncline
Shear thrust
Thrust Faults: a thrust sheet wherein dip flattens as it passes over a ramp
Fault-bend Folds
Thrust Faults: Form as layers fold during propagation of a thrust through a sedimentary sequence
Fault-propagation fold
Thrust Faults: Folds that forms near the thrust surface during movement
Drag folds
Thrust faults: piece material. the age of forse material is usually intermediate between the age of the HW and the FW
horse and slice
Thrust faults: the smaller faults in a group of thrust faults
Imbricate Thrust
Thrust faults: occurs when two subparallel thrust approximately of equal displacement are separated by a deformed interval that is thin relative to its total area extent
Duplex
Thrust faults: The upper of the two master faults
Roof thrust
Thrust faults: The lower of the two master faults
Floor thrust
Thrust faults: the line of intersection of two fault surface
Branch line
Thrust faults: thrust fault that is terminated at the surface due to erosion
Erosion or Emergent thrust
Thrust Faults: a thrust fault that does not manifest into the surface
Blind Thrust
Features produced by erosion: Dismemberment of a thrust sheet by erosion
Klippe
Features produced by erosion: A large remnant. Also used for a large single thrust sheet
Allochthon
Features produced by erosion: involve transport of metamorphic or igneous rocks or both as part or all of a thrust sheet
Crystalline Thrust
Sinistral
Left Lateral strike slip fault
Dextral
Right Lateral strike slip fault
bound the edge of thrust sheets
Tear fault
Right step overs or Left step overs
Pull apart or Rhomb-graben or Rhombchasm
Right-step overs sinistral fault or left step over dextral fault
Push up or Rhomb horst
faults which converge or project toward a single point
Radial faults
faults which form coencentric to a point
Concentric faults
faults which follow bedding or occur parallel to the orientation of bedding plane
Bedding faults/bedding plane faults
A large strike slip fault that segments plate boundaries or create plate boundaries, they connect two MOR or destructive plate boundaries, it can get very long just like the San Andreas Fault
Transform Fault
True or False: Large transform fault are actually fault zones rather than large individual fault
True
True or False: transfer fault are bounded and cannot grow freely implying that their displacement increases relative to their strength
True
Strike slip faults that have free tips and not constrained by any other structures, their free tips move so that the fault length increases as displacement accumulates
Transcurrent Faults
Free strike slip faults form within plates
Intraplate faults
Free strike slip faults that occur along plate boundaries
Interplate faults
True or False: Transcurrent faults can be expected to meet and interfere with other faults at some point during their growth history, but they will never have the special kinematic role that transform faults have
True
True or False: (Single Faults (SIMPLESHEAR)) strike slip faults forms when individual parts of the crust move at different rates along the surface of the earth
True
an experiments that models different secondary structures associated with strike slip fault
Riedel’s clay experiments
Strike slip faults that were active and formed at about the same time under the same regional stress field
Conjugate strike slip faults (Pure shear)
True or false: Conjugate faults result from pure shear in the horizontal plane where shortening in one direction is compensated by orthogonal extension in the vertical direction
True
when an individual fault segments overlap and link, a local deviation from the general fault trend is established in the form of
Fault step over or Fault bend
True or False: Contractional or extensional structures form in such bends is dependent on the sense of slip on the fault relative to the sense of stepping
True
Contractional or extensional? includes stylolites, cleavages, folds, and reverse faults that form in restraining bends as this bends are areas of positive relief
Contractional structures
Subparrallel reverse or oblique slip contractional faults bounded by the two strike slip segments can form and called
contractional strike-slip duplexes
Produces extentional structures such as Normal faults and extension fractures
Releasing bends
Parallel extensional faults bounded on both sides by strike-slip faults are called
extensional strike slip duplexes
Give clues for dectecting of releasing and restraining bends in the field since seismic not alone can detect them
normal faults, reverse faults and folds
A characteristic feature of such bends is their tendency to split up and widen upward is called
flower structures
Flower structures that are associated with restraining bend are called
positive
Flower structures that are associated with releasing bend are called
negative
Bends in strike-slip faults can produce local components of contraction or extension,they can dominate the full length of the fault if it is shear zone or strike slip fault if the fault is not purely strike slip this type of deformation occuring in such bends are reffered as
Transpression and Transtension
is the spectrum of combinations of strike slip and pure contraction
Transpression
is the spectrum of combinations of strike slip and extension
Transtension
the extend of PFZ
-1250 km
whats the trend of PFZ
NNW
The movement of PFZ
Left lateral strike slip fault
1990 Luzon Earthquake
7.8
1645 Luzon earthquake
7.5
1968 Casiguran earthquake
7.3
2013 Bohol earthquake
7.2
1994 Mindoro earthquake
7.1
2012 Visayas earthquake
6.9
1983 Luzon earthquake
6.5
1976 Moro Gulf earthquake and tsunami
8.0
2012 Samar earthquake
7.6
surface manifestation associated with salt domes
Radial expansion faults and Concentric collapse faults
state criteria for faulting
- Repetition and ommission of stratigraphic units, or the displacement (offset) of a recognizable marker
- Truncation of structures, beds or some rocks units against some feature
- Occurences of fault rock such as mylonites and cataclasites
- Abundant of veins, silicification or other mineralization along afracture zone
- Drag
- Slicken sides or slickenlines
- Fault scarp
Fault scarp is evolved to _____ through differential erosion through time along the fault which will level the topograpic surface and may remove a resistant layer in the HW.
Fault line scarp
a fault line scarp which erosion preserves the original facing direction of the fault scarp
Resequent Fault line Scarp
a fault line line scarp that through erosion of a resistant layer faces opposite the direction fault scarp. An incorrect motion sense would be inferred on topography alone
Obsequent Fault line Scarp
True or False: “lubricating” effect of fluid in afault zone is really a bouyancy effect that reduces the shear stress necessary to permit the fault slip as the fluid pressure reduces the normal stress on the fault plane which result to the effective normal stress
True
involves sudden movement on the fault after long term accumulation of stress, elastic rebound; causes of earthquake
Stick slip (unstable frictional sliding)
uninterrupted motion along the fault; so that stress is relieved continoulsy and does not accumulate
Stable sliding (continous creep)
