Earthquake Triggering at Oceanic Transform Faults

Posted on 08.25.2015
Modified USGS Map illustrating the mid-ocean ridge system. Dark lines are oceanic transform faults. Oceanic transform faults have a large effect on how new crust is formed and also affects spreading at mid-ocean ridges.

Three-fifths of the Earth’s surface is comprised of oceanic crust, all of which has been formed at mid-ocean ridges. The mid-ocean ridge system on Earth, is often compared to the seams of a baseball wrapping around the planet. One of the most ubiquitous features along the ridge system are the transform fault offsets, which, in our baseball analogy, are the stitches. There are more then 150 transform fault offsets around the world, but as the majority are thousands of meters beneath under water, only a handful have been studied in detail.

The primary focus of my PhD work was trying to better understand the dynamics of oceanic transform faults. One of the first projects I developed as a graduate student was investigating earthquakes recorded along segmented transform faults. As with faults on land, oceanic transform faults are often broken up into several smaller fault strands. We found that the segmentation of oceanic transform faults plays a large roll in the dynamics of the earthquakes that rupture them.

In particular, offsets can effect the maximum size of earthquakes by decreasing the ductile area available for earthquake rupture, and by preventing and can also effect how separate fault strands along a single transform communicate with each other. To tackle this problem, we used a combination of seismic data analysis from the East Pacific Rise, simple 2D thermal models and Coulomb static stress modeling to show how segmentation is important for earthquake processes.

COLLABORATORS: Jian Lin (WHOI), Debbie Smith (NSF / WHOI)

FUNDING: This work was funded by a National Science Foundation Graduate Research Fellowship (Gregg)