Seismology of the MOR

• Earth’s crust is moving and faulted

• Earthquakes happen along belted regions

• In 1965, the theory of Transcurrent Faults along the MOR was challenged by Wilson

Alex TurnerDina FreedmanGEOG 695011.22.11

Transform Faults• Earthquakes at transform faults are generally shallow• Cannot exist unless there is crust displacement• They are large enough to map (some segments 200 to 800

km)

The transform fault appears here as the long narrow bands that link the end of segments (Macdonald and Fox, 1990)

Focal Mechanisms

• A Focal mechanism can be derived from observing the pattern of "first motions”

• Do the first arriving P waves break up or down?

Focal Mechanisms

Magnitude 5.3 NORTHERN MID-ATLANTIC RIDGE Friday, November 18, 2011 at 06:00:54 UTC

Seismicity

Magnitude 5.3 NORTHERN MID-ATLANTIC RIDGE Friday, November 18, 2011 at 06:00:54 UTC

Summery of Evidence• Shallow Earthquakes• Earthquakes confined to ridge crests and

the areas in-between offset ridge crests.• Presence of Earthquake Swarms