Earth, Molnar 2015 3x

What are fracture zones?

Long linear scars on the seafloor formed by offset mid-ocean ridges.

How are fracture zones formed?

By offset segments of mid-ocean ridges during seafloor spreading.

What is a transform fault?

Active part of a fracture zone between ridge segments where plates slide past.

What is the difference: transform fault vs fracture zone?

Transform fault is active; fracture zone is inactive scar beyond ridge offsets.

How are mid-ocean ridges shaped?

Zig-zag due to offset ridge segments linked by transform faults.

Who proposed fracture zone interpretation (1965)?

J. Tuzo Wilson.

What happens to inactive parts of fracture zones?

They are carried away from ridge and become inactive “scars”.

Why are fracture zones long and linear?

They preserve motion direction as plates diverge over time.

Where are earthquakes concentrated in fracture zones?

Only on active transform fault segments between ridge offsets.

Why don’t fracture zones always show earthquakes?

Most of the zone is inactive and moves with one plate.

What is sense of slip?

Direction one side of fault moves relative to the other.

How is slip direction measured in oceans?

Indirectly using seismic P and S wave first-motion analysis.

What are nodal planes?

Imaginary planes separating compression and dilation in seismic waves.

What is key difference in P-wave patterns?

Compression vs dilation reveals fault mechanism and slip direction.

Why are transform faults important in plate tectonics?

They link ridge segments and confirm plate motion geometry and spreading symmetry.