[SIO GP Seminars] Geophysics Seminar: Mladen Nedimovic

[Karen Luttrell]

Join us today, Friday May 5th, for Geophysics Seminar series.

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Friday, May 5, 3:00 PM 
(refreshments served at 2:45 PM) 
Munk Conference Room 

Mladen Nedimovic
Lamont-Doherty Earth Observatory

 Structure and evolution of the oceanic Juan de Fuca plate from 
accretion to subduction

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ABSTRACT
The region comprising the northeast Pacific Ocean and the Cascadia 
margin is a natural laboratory for studies of various tectonic and 
geologic processes of global importance. Seafloor spreading, slab 
bending and hydration, oceanic subduction and interplate coupling, and 
slab dehydration and intraslab seismicity are some of the many 
processes that occur within a distance of only several hundred 
kilometers. I will first briefly describe the study area, the general 
crustal structure, and the operating tectonic and geologic processes. 
Then, I will focus on presenting and interpreting three specific 
observations that can be made by analyzing seismic reflection images. 
In the direction of increasing crustal age these are: Reflections from 
localized thick Moho transition zones, normal faulting seaward from the 
trench, and variable megathrust reflectivity. Imaged thick Moho 
transition zones appear to provide support for the existence of complex 
magmatic plumbing systems at mid-ocean ridges and for the crustal 
generation hypothesis from multiple magma bodies. Extensional regimes 
seaward of subduction trenches and due to slab bending are likely the 
key for hydrating the approaching oceanic slabs but at the Cascadia 
margin this process appears to be mostly limited to the crust, possibly 
resulting in reduced occurrence rate and magnitude of intraslab 
seismicity. Variations in the character and thickness of the megathrust 
reflection package seem to provide a high-resolution method for mapping 
at least the landward end of maximum co-seismic slip during subduction 
earthquakes.
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