Geology 3120 Introduction to Strike-Slip Faults
Levant Strike-Slip Faults
Outline
•
Stick-Slip and Creep
•
Andersonian Theory
•
Kinematics
•
Strike-Slip Faults on Continental Margins
•
Strike-Slip Faults on Mid-Ocean Ridges
∆
Stick-Slip: Elastic Rebound Theory
Elastic Rebound Theory
•
Imagine a fence across an active
fault
Elastic Rebound Theory
•
Imagine a fence across an active
fault
•
Regional deformation occurs but
the fault does not break. The
fence becomes curved.
Elastic Rebound Theory
•
Imagine a fence across an active
fault
•
Regional deformation occurs but
the fault does not break.
•Once
the fault breaks, the fence
is sheared in half and marks offset
•Note
that far-field strain may limit
whether the fault accommodates
all the plate motion at its trace
Elastic Rebound Theory
Elastic Rebound Theory
QuickTime™ and a Cinepak decompressor are needed to see this picture.
Creep (Aseismic Slip)
•
Imagine a fence across an active
fault
•
Slip occurs slowly on the fault
continually over time.
•
Creeping faults do not store
elastic energy that might be
released by a stick-slip event (an
earthquake)
Andersonian Theory
Conjugate Strike-Slip Faults
Determining Sense of Slip
Right-Lateral (Dextral)
Left-Lateral (Sinistral)
Arrow Heads ( ) and Tails ( )
Block moving toward you like an arrowhead
heading towards you
Block moving away from you like seeing the
feathers of an arrow
Arrow Heads ( ) and Tails ( )
„
Right-lateral or left-lateral?
Arrow Heads ( ) and Tails ( )
„
Left-lateral
Arrow Heads ( ) and Tails ( )
„
Sinistral or Dextral?
Arrow Heads ( ) and Tails ( )
„
Dextral
Strike-Slip Faulting: Shallow Brittle vs Deep Shear
Strike-Slip Faulting: EQ’s = dislocations
See http://www.data.scec.org/Module/links/landrupt.html
Landers rupture propagation movies
Strike-Slip Faults on Continental Margins
N
50 m
„
What is the sense of slip?
Strike-Slip Faults on Continental Margins
N
50 m
„
Right-lateral (dextral)
Transtension
Development of a Pull-Apart Basin
Pull-Apart Basin
Initial Releasing Bend
Evolution of a Releasing Bend
Normal (-) Flower Structure - Tulip
Transpression
Development of a Restraining Bend
Initial Restraining Bend
Evolution of a Restraining Bend
Reverse (+) Flower Structure - Palm
Summary of Flower Structures - Palms & Tulips
Oceanic Strike Slip fault: Transforms
Strike-Slip Faults on Mid-Ocean Ridges
„
What is the sense of slip?
Strike-Slip Faults on Mid-Ocean Ridges
„
Right-lateral (Dextral)
Pacific-Antarctic Ridge
„
Magnetic anomalies from present to 9.9 Ma
„
Warm colors indicate positive polarity
„
Cool colors indicate reverse polarity