Fracture Zone quake
On Friday, a large earthquake occurred in a geologically interesting area of the mid-Atlantic ridge. The mid-ocean ridge system is a gigantic chain of mountains that stretches around the world on the ocean floor at the boundaries where plates are spreading apart.
The mid-ocean ridges aren’t just straight lines; they twist from side to side and are broken into segments that lock in the original shape of the plates. The oceanic rift zones themselves are dominated by normal faults, the kind that commonly occurs when two plates pull apart. To step sideways, a spreading center breaks into two segments with a strike-slip fault in-between, the type of fault that forms when one plate grinds past another.
The Charlie Gibbs fracture zone is an oceanic transform fault, a strike-slip fault on the ocean floor. On Friday, that fault broke, producing a magnitude 7 earthquake.
Because the rocks just were sliding past each other, side to side, there was no tsunami generated and since the quake occurred far out to sea there was no major damage, just a geologically interesting place for a strong earthquake. This fracture zone has produced several earthquakes of this size in the past 60+ years since humans have been actively monitoring seismic signals.
-JBB
Image credit: USGS http://on.doi.gov/1KTMeFx