10:30 AM10:30

Invited talk at UTIG

I was pleased to have the chance to visit UTIG (the University of Texas Institute for Geophysics) last week to talk about our new Bayesian inversion using multiple seismic data types. It was great to meet lots of the UTIG researchers and enjoy both science discussions  and Austin TX local brews (especially in combination)!

Title and abstract:

An adaptive Bayesian inversion for upper mantle structure using surface waves and scattered body waves

I will present a methodology for 1-D imaging of upper mantle structure using a Bayesian approach that incorporates a novel combination of seismic data types and an adaptive parameterisation based on piecewise discontinuous splines. This inversion algorithm lays the groundwork for improved seismic velocity models of the lithosphere and asthenosphere by harnessing the recent expansion of large seismic arrays and computational power alongside sophisticated data analysis. Careful processing of P- and S-wave arrivals isolates converted phases generated at velocity gradients between the mid-crust and 300 km depth. This data is allied with ambient noise and earthquake Rayleigh wave phase velocities to obtain detailed VS and VP velocity models. Synthetic tests demonstrate that converted phases are necessary to accurately constrain velocity gradients, and S-p phases are particularly important for resolving mantle structure, while surface waves are necessary for capturing absolute velocities. We apply the method to several stations in the northwest and north-central United States, finding that the imaged structure improves upon existing models by sharpening the vertical resolution of absolute velocity profiles, offering robust uncertainty estimates, and revealing mid-lithospheric velocity gradients indicative of thermochemical cratonic layering. This flexible method holds promise for increasingly detailed understanding of the upper mantle. 

Video: https://mediasite.jsg.utexas.edu/UTMediasite/Play/1e7dd1c3b83a492a85b289767b6fcd231d

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AGU 2017 Fall meeting - sessions on Rifts, LAB, and mantle melt
to Dec 15

AGU 2017 Fall meeting - sessions on Rifts, LAB, and mantle melt

I'm involved in convening three sessions at this year's American Geophysical Union Fall meeting (this year in New Orleans!):

The abstract portal is now open. Apply by August 2nd!

The three sessions I'm chairing/convening are linked below. It looks like it's going to be a fantastic meeting (and v. excited to explore New Orleans). Hope to see you there!


T005:  Breaking Up is Never Easy: Why Do Some Rifts Fail and Others Succeed?

The breakup of continents is a fundamental process of plate tectonics. However, we have not yet identified the crucial ingredients that permit complete rupture of strong continental lithosphere. Studies of continental breakup are biased towards success stories - rifts that evolve to oceanic spreading. Some extension episodes cease before this point, presumably in the absence of some fundamental process, initial condition(s), or forcing. Investigations of “failed rifts” may help isolate key processes or conditions that enable continental breakup, particularly when compared to successful examples. Outstanding questions include: Does rift success/failure depend on intrinsic or far-field properties? How do pre-existing structure, magma, and volatiles influence rift initiation, continuation, and extinction? Are failed rifts actually “paused rifts” that can later be reactivated? Do analogous mechanical controls apply to extinct seafloor spreading centers? We solicit contributions from diverse geoscience perspectives, including geodesy, geodynamics, geochemistry/petrology, volcanology, structural geology and seismology.


DI006:  Diverse perspectives on the lithosphere and the asthenosphere

The lithosphere-asthenosphere boundary (LAB) separates Earth’s rigid tectonic plates from the underlying convecting mantle. Tractions, thermal gradients, compositional differentiation, fluid/melt accumulation, crystallographic fabrics, and grain size heterogeneity have all been suggested to occur at (or near) this interface. How this boundary is expressed in different tectonic settings and how it relates to other seismic and magnetotelluric discontinuities including the Moho and mid-lithospheric discontinuities (MLDs) is a topic of ongoing vigorous debate. We will focus on the lithosphere-asthenosphere system in a variety of settings including but not limited to continents, oceans, margins, rifts, ridges, hotspots, plumes, and subduction zones. We welcome research contributions from diverse fields, including but not limited to seismology, magnetotellurics, petrology/mineralogy, dynamical modelling, and mineral physics.


DI009:  Interdisciplinary Perspectives on Mantle Melting and Volcanism

Melting within the Earth, across a range of depths, has fundamental consequences for planetary dynamics and evolution. Yet, questions regarding source composition, melt migration and distribution, in situ melt fraction, and magma storage and evolution remain unanswered. We invite contributions from studies of asthenosphere/lithosphere melting in various tectonic environments (e.g., mid-ocean ridges, subduction zones, hotspots), as well as deep planetary melting (e.g., transition zone, magma ocean). Topics covered by this session include: (1) magmatic processes in the presence of volatiles and heterogeneous rock assemblages, (2) melt migration and melt-rock interaction, (3) melting and solidification at the core-mantle boundary, (4) imaging melt within the Earth through seismic or magnetotelluric approaches, (5) plume vs. non-plume origin of intraplate volcanism, and (6) magmatic processes and the evolution of magmas in the early Earth. We solicit research that combines the strengths of geochemistry, petrology, geology, geodynamics, geophysics, and mineral physics.


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