Strike-Slip Tectonics

Jyr-Ching Hu, Department of GeosciencesNational Taiwan University

San Andreas fault near Los Angeles

Landsat image + Shuttle Radar Terrain Mission (SRTM)

http://epod.usra.edu/archive/images/losangeles.jpg, NASA/JPL/NIMA (SRTM Mission)

http://epod.usra.edu/archive/images/losangeles.jpg

San Anderasfault zone

Boundary of Pacific Plate and North American Plate

美國西部加州的San Andreas Fault是界開北美洲板塊與太平洋板塊之間的轉形斷層。

Alpine Fault in New Zealand

M: Macquarie TrenchTK: Tonga-Kermadectrench

紐西蘭的Alpine Fault是界開印度澳洲板塊與太平洋板塊之間的轉形斷層。

Dead Sea Transform (DST)

http://www.see.leeds.ac.uk/

Sinai from Space

http://epod.usra.edu/archive/images/sinaism.jpg

Sinai Peninsula from Egypt on the left to Saudi Arabia on the right. The Gulf of Aqaba is a finger of the Red Sea bottom center, pointing north to the Dead Sea, the small body of water near the center of the view. The Gulf of Suez appears in the lower left corner. Northwest Saudi Arabia occupies the lower right side of the view

NASA Human Space Flight

http://spaceflight.nasa.gov/

Transpression and Transtension

• Transpression (橫移壓縮): Occurs where there is a combination of strike-slip movement and shortening, and can produce uplift along the fault

• Transtension (橫移伸張): Occurs where there is a combination of strike-slip movement and and shortening, and can produce subsinence along the fault

Transform (轉型斷層) versus Transcurrent faults (橫移斷層)

Two kinematic classes: Transform and transcurrent faults1. Geometry of its endpoints (the locations along strike where the fault terminate)

2. Slip magnitude varies along the fault’s length

3. Fault’s geometry evolves through time

Transform fault linking two convergent plate boundaries

斷層兩端為聚合型板塊邊界的轉型斷層

斷層兩端為分離型板塊邊界的轉型斷層

Length of a transform fault can change with time

(b) 如果斷層的兩端分別為分離型板塊與聚合型板塊邊界，若板塊擴展的速率比另一端板塊隱沒的速率快的話，則轉型斷層的長度會變長。

(a) 如果斷層兩端是分離板塊邊界，而兩端分離板塊擴展的速率是一樣，則轉型斷層的長度不變。

(c) 如果斷層的一端是三接點，而此三接點(T)會隨著時間而移動的話，則轉型斷層的長度會變長。

當轉型斷層的長度不變或變短時，則沿線的位移量保持不變。(a) 如果斷層的長度保持不變的話，斷層線上X點的位移量與Y點的位移量是相同的。

(b) If the transform length change with times, then amount of slip varies along the length. At time 1, the fault is fairly short. At time 2, the length of the fault is longer. Displacement at X, is greater than displacement at point Y.

The amount of slip on a transform can exceed the length of the transform在此，總位移量指的是中洋脊開始擴展以來轉型斷層兩側同時形成的岩石之間的距離

The amount of slip on a transform can exceed the length of the transform

Termination along transcurrent fault

Transcurrent faults (橫移斷層)(a) 右移的橫貫斷層兩端為馬尾狀(horsetail) 正斷層系列

(b) 右移的橫移斷層兩端為馬尾狀逆斷層系列

Growth of transcurrent fault

1. As time passes, the fault lengthens, and the displacement on the fault increases.

2. In the process, some horesetailsplays are abandoned.

3. Note that the markers just beyond the tips of the fault are starting to bend, prior to rupturing.

4. Note also that the displacementon the fault is less that the lengthof the fault.

轉型斷層 (Transform fault) 與橫移斷層(Transcurrent fault)的區別

Transform fault Transcurrent fault

斷層兩端的幾何型態

兩端點突然與其他的地質構造連接。

到端點會消失掉而轉變成塑性應變帶，或分散成為一系列的小斷層。

斷層沿線滑動數量變化的方式

斷層沿線的滑動數量可以比斷層長度長、短或相同。

從一點開始擴展，斷層長度隨著位移的增加而變長。斷層的位移量一定比斷層的長度小

斷層的幾何型態隨著時間演變的方式

斷層沿線各點的滑動數量可以是一樣的

斷層的位移量在斷層線的中心最大，向兩端逐漸變小。

Faults of southern California

1. Note that faults anastomose and that, locally, folds form adjacent to the faults.

2. Note that large bend in the San Andreas Fault at its intersection with Garlock Fault.

A stepover (躍階) along a strike-slip fault

躍階Stepover Ridge(山脊)

Depression(凹陷)Dextral Shear can be distributed along fault segments that are not coplanar. Slip is relayed from one segment to another as a stopover.

Restraining stepover

Releasing stepover

Arrays of subsidiary structures associated

with dextral shear

(a) Subsidiary strike-slip fault (Riedel shear: R and R’)

(b) En échelon folds and En échelon thrusts.

(c) En échelon folds which formed and then were later offset by shear on a strike-slip fault.

(d) En échelon normal faults and veins.

李海兵 中國地質科學院地質研究所大陸動力學實驗室

沿地表破裂带出露的挤压鼓包（高>1m）的初步统计

不对称 对称 不对称

107 19 11

李海兵 中國地質科學院地質研究所大陸動力學實驗室

李海兵 中國地質科學院地質研究所大陸動力學實驗室

李海兵 中國地質科學院地質研究所大陸動力學實驗室

李海兵 中國地質科學院地質研究所大陸動力學實驗室

李海兵 中國地質科學院地質研究所大陸動力學實驗室

A laboratory model of strike-slip development

Clay: Weak uppermost crustWood: Stronger lower crust

A laboratory model of strike-slip development

R and R’: Riedel shears

P: P fractures

A later stage of deformation, in which Riedel shears have been linked by P fractures.

Strain model explaining the origin of subsidiary structures along a strike-slip fault

(a) Simple shear: A square becomes a parallelogram. A circle in the square becomes an ellipse.

(b) Detail of strain ellipse: Folds and thrusts form perpendicular

to the shortening direction.Normal faults and veins form

perpendicular to the extension direction.

R and R’ shears form at an acute angle to the shortening direction.

(cf. Fig. 19.12)

Strain model explaining the origin of subsidiary structures along a strike-slip fault

(c) Note that R and R’ are similar to conjugates shear fracturesformed in rock cylindersubjected to an axial stress.

(d) You can simulate formation of en échelon folds with a sheet of paper.

A cross-section of a pressure ridge

San Andreas fault near Palmdale, California

Transpression (橫移壓縮)and transtension(橫移伸張)

(a) When blocks shear and squeeze together(transpression).

(b) When blocks shear and pull apart (transtension), sand sags.

Positive and negative flower structure

在橫移伸張斷層帶內部所形成的正型開花構造(Positive flower structure)副斷層為逆滑斷層

在橫移伸張斷層帶內部所形成的負型開花構造(Negative flower structure).副斷層為正滑斷層

Restraining and releasing bends

Map-view models of fault bends along strike-slip faults. The “edges” of the crustal blocks are provided for reference.

(a) Releasing bend at which normal faults and a pull-apart basin have formed.

(b) Restraining bend at which thrust faults have formed.

The San Andreas Fault bends along the margin of the Mojave Desert

Dashed lines: Outline imaginary reference blocks

Strike-slip duplexes

Map view

Strike-slip duplexes: An array of several faults that parallels a bend in a strike-slip fault. Strike-slip duplexes formed at restraining bends can be called transpressiveduplexes, while those formed at releasing bends can be called transtensile duplexes.

Deep-crustal strike-slip fault Geometry

A regional-scale strike-slip fault may consist of a broad zone of brecciaand gouge at shallow crustal levels. At deeper layer, the zone may narrow into a zone of cataclasite, and at great depth, it broadens into a zone of mylonite.

The shallower portion of some strike slip faults may be offset, relative to the deeper portion, by a detachmentat depth.

Collision in southern Asia:

Oblique collision

Strike-slip faulting at an oblique convergent margin

At oblique-convergent plate margins, the relative motionbetween the two plates can be partitioned into a component of dip slip motion (thrusting) perpendicular to the margins, and a component of horizontal shear (strike-slip faulting) parallel to the margin.

Progressive stages during oblique docking of an exotic terrane (外來岩體)

板塊運動的方向與板塊邊界斜交時，平行板塊邊界走向的滑動分量(strike-slip component)所造成的平滑斷層可以使因為碰撞而添加在原地大陸的外來岩體(exotic terrane)錯開。

Lateral escape: Eastern Mediterranean to the Caspian Sea

阿拉伯板塊向北運動擠壓土耳其沿著North Anatolian平滑斷層與East Anatolian平滑斷層向西逃逸。

Lateral ramp and tear fault (撕裂型斷層)

tear fault tear fault

Lateral ramp: 側邊斷梯

Flat: 斷階

Frontal ramp:前邊斷梯

Makran fold-thrust in Pakistan

巴基斯坦境內Makran褶皺逆衝斷層帶內部的共軛平滑斷層

Block model of the Garlock faultThe Garlock Fault in southern California is one of the largest examples of a strike-slip within a rift environment.

Topographic of the Clipperton fracture zone (FZ) and transform zone (TZ) of the East

Pacific Rise

EPR: East Pacific Rise

Assignment

• Chapter 21.2: The Tibetan Plateau and surrounding regions: An essay by Leigh H. Royden and B. Clark Burchfiel

Strike-Slip TectonicsSan Anderas fault zoneAlpine Fault in New Zealand Dead Sea Transform (DST)Sinai from Space Transpression and TranstensionTransform (轉型斷層) versus Transcurrent faults (橫移斷層)Transform fault linking two convergent plate boundariesLength of a transform fault can change with timeThe amount of slip on a transform can exceed the length of the transformThe amount of slip on a transform can exceed the length of the transformTermination along transcurrent faultGrowth of transcurrent fault轉型斷層 (Transform fault) 與橫移斷層 (Transcurrent fault)的區別Faults of southern CaliforniaA stepover (躍階) along a strike-slip faultArrays of subsidiary structures associated with dextral shear A laboratory model of strike-slip developmentA laboratory model of strike-slip developmentStrain model explaining the origin of subsidiary structures along a strike-slip faultStrain model explaining the origin of subsidiary structures along a strike-slip faultA cross-section of a pressure ridge Transpression (橫移壓縮)and transtension (橫移伸張)Positive and negative flower structureRestraining and releasing bendsThe San Andreas Fault bends along the margin of the Mojave DesertStrike-slip duplexesDeep-crustal strike-slip fault GeometryCollision in southern Asia: Oblique collisionStrike-slip faulting at an oblique convergent marginProgressive stages during oblique docking of an exotic terrane (外來岩體)Lateral escape: Eastern Mediterranean to the Caspian SeaLateral ramp and tear fault (撕裂型斷層)Makran fold-thrust in PakistanBlock model of the Garlock faultTopographic of the Clipperton fracture zone (FZ) and transform zone (TZ) of the East Pacific RiseAssignment