[unav_all] REMINDER - IRIS WEBINAR: Anisotropic Seismic Tomography and the Gutenberg Discontinuity - 2/26, 2 PM Eastern

Andy Frassetto andyf at iris.edu
Tue Feb 25 07:44:01 MST 2014

"New Constraints on the Nature of the Gutenberg Discontinuity from 
Anisotropic Seismic Tomography" will be presented at 2 pm EST (7 pm UTC) 
on Wednesday, 2/26.

Register *only* if you intend to watch the live webinar: 

You will be emailed a confirmation containing a link for watching the 
live broadcast. A recording will be subsequently posted here: 
http://www.youtube.com/user/IRISEnO. Access to older webinars, along 
with related materials and more information on the series is found here: 

Presenter: Dr. Caroline Beghein, Assistant Professor, University of 
California-Los Angeles

Abstract: The origin of the lithosphere-asthenosphere boundary (LAB) 
remains enigmatic. Tomographic studies argue in favor of a thermal LAB, 
but detections of the Gutenberg (G) seismic discontinuity, often 
associated with the LAB, cannot be explained by thermal effects alone. 
In this study, we modeled 3-D seismic anisotropy and velocity in the 
Pacific upper mantle and compared our models with the location of SS 
precursor detections of the G. Our results are consistent with a purely 
thermal LAB, but we found that the G is associated with vertical changes 
in anisotropy within the lithosphere. This implies that the two are not 
equivalent interfaces even though they may overlap in some locations. We 
propose that the G results from dehydration under mid-ocean ridges, 
generating a depleted, viscous layer that becomes overprinted by lowered 
temperatures as the plate cools down. Partial melt may also be present 
at the LAB where the two interfaces coincide and help explain enhanced 
detections of the G near upwellings.

Please direct any related questions or the name of your favorite seismic 
station to Andy Frassetto (andyf at iris.edu).

System Requirements
PC-based attendees: Windows® 8, 7, Vista, XP or 2003 Server
Mac®-based attendees: Mac OS® X 10.6 or newer
Mobile attendees: iPhone®, iPad®, Android^(TM) phone or Android tablet
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