Seeing Through Rocks: Seismic Imaging of the Cascadia Subduction Zone

[Viva_La_Revolution]

August 3, 2012
by Kate Allstadt

I recently returned from two weeks at sea aboard the research vessel, the R/V Marcus G. Langseth, where I was fortunate to be a part of the Cascadia Open Access Seismic Transects research cruise. The scientific objective of the cruise was to obtain high quality seismic images of the Cascadia subduction zone: the interface between the downgoing Juan de Fuca plate and the overriding North American plate that can generate the magnitude ~9 megathrust earthquakes that we’re always talking about.

The technology we used, called “reflection seismology,” is the sort of technology that oil companies use to search for oil reservoirs. Basically, we send seismic waves into the earth and the waves bounce off the contrasts between different rocks in the subsurface. We record these reflections with seismometers and turn them into an image, allowing us to see into the earth and study the subsurface. This can be done on land or at sea.

more with images and charts --> http://www.pnsn.org/blog/2012/08/03/seeing-through-rocks-seismic-imaging-of-the-cascadia-subduction-zone

[On the Road]

1. This is Very Cool

Is the subducting plate in that area also moving north (following Alaska) in addition to simply diving underneath?

[Viva_La_Revolution]

2. yes, the west side of the juan de fuca is getting northward pressure from the pacific plate

while the north east side subducts under the north american plate. there's a theory out there that the northward push is lessening the pressure to subduct, and turning the subduction zone into a transom fault.