3D Extension at Plate Boundaries Accommodated by Interacting Fault Systems

Area of Science:

• Structural Geology
• Tectonics
• Geophysical Modelling

Background:

• Traditional explanations for complex normal fault patterns involve multiple 2D deformation phases.
• Alternative theories propose simultaneous fault set development in 3D deformation.
• Pre-existing structures are often considered crucial for complex fault geometries.

Purpose of the Study:

• To investigate the development of normal faults under 3D extension using analogue models.
• To determine if faults develop simultaneously or alternately during 3D deformation.
• To explain complex fault patterns observed in tectonic settings through stress-driven interactions.

Main Methods:

• Analogue modelling of normal faults under controlled extension.
• Simulating 3D extensional deformation without pre-existing structures.
• Analyzing stress interactions and fault development patterns.

Main Results:

• 3D extension preferentially leads to the alternate development of faults with different trends, not simultaneous formation.
• Stress-driven interactions partition deformation into coupled fault systems.
• Radial extension produces curvilinear grabens and perpendicular faults, matching Afar observations.
• Alternate perpendicular fault development explains rift-shear margin patterns, as seen in the Barents Sea.

Conclusions:

• Complex normal fault patterns can arise from the alternate development of faults during a single phase of 3D extension.
• Stress interactions are key to partitioning deformation and forming coupled fault systems.
• Analogue models successfully replicate natural fault patterns observed in diverse tectonic settings.