Virtual Seminar Series - IGCP 648 Supercontinent Cycles & Global Geodynamics

Delamination of oceanic lithosphere: a key for subduction initiation?

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Speaker: João Duarte (Ciências ULisboa).

Speaker bio: João Duarte works in tectonics, geodynamics and marine geology. He is an Assistant Professor at the University of Lisbon, where he coordinates the research group on Continental Margins and the Deep Ocean Frontier, and the EarthSystems Doctoral School from the Instituto Dom Luiz (IDL). He completed his PhD at the University of Lisbon in 2012. In 2011, he moved to Melbourne for a Post-Doc at Monash University where he stayed until 2015.
João has edited several works, which include an AGU geophysical monograph entitled “Plate Boundaries and Natural Hazards”, an Elsevier book entitled “Transform Plate Boundaries and Fracture Zones” and an Elsevier special volume on the “200 years of geodynamic modelling”. He was awarded in 2011 an IPGP Foreign Student Award for outstanding PhD research, in 2015 he won the Discovery Early Career Researcher Award from the Australian Research Council, and in 2017 he was given the Arne Richter Award for Outstanding Early Career Scientists of the European Geosciences Union. João is passionate about science communications and he regularly collaborates with science magazines and the media.

Abstract: On the 1st of November 1755, a giant 8.7 magnitude earthquake struck off the coast of Portugal, destroying the city of Lisbon and causing great alarm all across Europe. In 1969, another 7.9 magnitude earthquake struck in the same region. Since then, many studies have been dedicated to the Atlantic margin of Portugal and several scientists proposed that this region may represent a unique case of incipient subduction in the Atlantic. Intriguingly, the epicenter of the 1969 earthquake occurred in a relatively flat abyssal plain, far from any known tectonic faults. Our studies have shown the existence of a seismicity cluster precisely below this plain at lithospheric mantle depths of ∼50 km, and tomographic models have consistently imaged a fast-velocity anomaly extending up to a depth of 250 km. We interpret this anomaly as a lithospheric drip caused by the delamination of oceanic lithosphere. We have tested this hypothesis with numerical models and they show that under certain circumstances oceanic lithosphere can indeed delaminate. Delamination of old oceanic lithosphere near passive margins may constitute a new class of subduction initiation mechanisms, with fundamental implications for the dynamics of the Wilson cycle.

The seminar will be approx. 1 hour (30 - 40 minute talk followed by questions/discussions).
We encourage participants to share their webcam footage so that the presenters can see the audience, but this is completely optional.
The talk will be recorded if agreed by the presenter and a link will be sent around soon after the talk.
We have a detailed code of conduct here that participants must agree to.

Seminar info:

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Meeting ID: 998 6891 1703
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