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"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.
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Register <b class="moz-txt-star"><span class="moz-txt-tag">*</span>only<span
class="moz-txt-tag">*</span></b> if you intend to watch the live
webinar: <a class="moz-txt-link-freetext"
href="https://www2.gotomeeting.com/register/368171466">https://www2.gotomeeting.com/register/368171466</a>
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You will be emailed a confirmation containing a link for watching
the live broadcast. A recording will be subsequently posted here: <a
class="moz-txt-link-freetext"
href="http://www.youtube.com/user/IRISEnO">http://www.youtube.com/user/IRISEnO</a>.
Access to older webinars, along with related materials and more
information on the series is found here: <a
class="moz-txt-link-freetext"
href="http://www.iris.edu/hq/webinar/">http://www.iris.edu/hq/webinar/</a>
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Presenter: Dr. Caroline Beghein, Assistant Professor, University of
California-Los Angeles
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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.
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Please direct any related questions or the name of your favorite
seismic station to Andy Frassetto (<a
class="moz-txt-link-abbreviated" href="mailto:andyf@iris.edu">andyf@iris.edu</a>).
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System Requirements
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PC-based attendees: Windows® 8, 7, Vista, XP or 2003 Server
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Mac®-based attendees: Mac OS® X 10.6 or newer
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Mobile attendees: iPhone®, iPad®, Android™ phone or Android tablet
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