Current projects:

  • Imaging small-scale convection beneath the Pacific Ocean (a part of the international PacificArray initiative)  All deformation on the surface of Earth, including faulting responsible for earthquakes, is produced by the motion of tectonic plates. It is widely accepted that thermal convection in the mantle drives plate motion, but details of that convection and how exactly it moves the plates are poorly understood. Oceanic plates make up 70% of the Earth's surface and offer important windows into mantle convection, yet they are largely unexplored due to the lack of seismic data from the ocean basins. Questions abound regarding the thermal structure of oceanic plates, the significance of volcanism in the middle of oceanic plates, and how the convecting mantle beneath the plates controls their movements. Waves in the gravity field and un-explained shallowing of the ocean floors hint at small-scale convection beneath the oceanic plates. Working with Jim Gaherty and Göran Ekström (LDEO) and Don Forsyth (Brown), our research project contributes to an international effort to strategically place temporary arrays of instruments across the Pacific Ocean basin that record the energy from earthquakes. Recent community advances in ocean bottom seismographs will be used to record unique datasets in locations where large gaps in coverage exist today. These data will allow us to infer deformation and variations in mantle temperature related to small-scale convection. As part of the international collaboration, all data will be openly available to scientists worldwide. Between 2018 and 2020, we went to sea four times (about 130 days in all!) to deploy two broadband Ocean ?Bottom Seismometer arrays in the central and then southwestern Pacific (read much more here). These phenomenal data sets hold huge potential to advance our understanding of the Pacific mantle, from Moho to core! This project is funded through NSF grant OCE-1658214.

  • Understanding the Main Ethiopian Rift, from axis to flank  Continental rifting is a fundamental part of the plate tectonic cycle, and lies at the nexus of geothermal and mineral resources, seismic and volcanic hazards, and geophysical research. Substantial variation between rift zones worldwide indicates that continental breakup is dictated by a complex interplay of tectonic forces and geologic characteristics. Therefore, it is critical to understand the full context for a rifting system, from the highly extended rift center that houses volcanoes and earthquakes to the flanks of the rift, where extension is just beginning and pre-rift structures are still evident. The Main Ethiopian Rift segment of the East Africa rift is perhaps the world’s most iconic continental rift. Working with a new dataset collected by my collaborator Katie Keranen (Cornell) I'm applying advanced  imaging techniques that use seismic data spanning this rift. Our objectives are to reveal the 3-D internal structure of this rift and shed light on key geologic processes in this and other rifts around the world. This project involves collaboration with scientists from Ethiopia and is funded through NSF grant EAR-1723170.

  • Lithosphere-scale imaging of the Eastern North American Margin (ENAM)  The ENAM has experienced several large-scale deformational events spanning multiple episodes of supercontinent assembly and breakup. A nearly un-interrupted tectonic history since the breakup of Pangaea has left behind an invaluable record of processes involved in the evolution from initial rifting and breakup to the mature margin present today. This project aims to unravel the deformational history of the ENAM using seismological imaging and observations of seismic anisotropy to understand the temporal progression of the margin. In particular, we are trying to shed light on two fundamental scientific questions related to the structure, evolution, and on-going dynamics associated with the eastern North American passive rift margin: 1) What is the structure of the lithosphere from top to bottom across the ocean-continent transition and how was it shaped by rifting processes? 2) What is the history of deformation both within and seaward of the passive margin, and how is present- day mantle flow controlled by the margin’s structure? This project combines an “amphibious” seismic broadband dataset with cutting-edge geophysical inverse techniques and complements ongoing GeoPRISMS community efforts. This project is funded through NSF grant EAR-1753722. 

  • Measuring mantle attenuation in Alaska I'm working to understand body wave velocity and attenuation beneath the state of Alaska, which has recently been illuminated by the USArray Transportable Array. We are building a comprehensive database of body wave attenuation measurements across Alaska, and inverting them tomographically in concert with velocity data.

  • Geodynamical models of mantle convection with dynamically evolving grain size  We harness experimentally derived scaling relationships to turn the output of our collaborators' fantastic dynamical models (giving temperature, pressure, and grain size that evolves with stress) into predictions for the things we'd seismically observe (wave speed, attenuation). This gives us a tool to quantitatively compare the model outputs to each other and to the real Earth. We find that we can constrain some of the important parameters in the lower mantle. We also learn that tradeoffs between grain size and temperature mean that standard interpretations of tomographic models might be significantly under-estimating temperature variations in the mantle.

  • Imaging cratonic structure in the Northern Central US  Working with Karen Fischer, I'm developing a joint inversion of S-p and P-s receiver functions, surface wave phase velocities, and a variety of other data types to pin down the 3-D velocity structure of the continental lithosphere. We are focusing on the deep structure of the cratons and continental interiors, from “lower-48” North America to Alaska to South Africa. We are particularly interested in constraining the character of the (seismic) lithosphere-asthenosphere boundary, and its implication for the long-term evolution and stability of continental interiors. 

Research areas:

Structural seismology

 

Vertical slice through tomography model from Eilon et al. [2015] showing slow (red) rift axis, and local seismicity.

Inverse theory

 

Most geophysical research rests either implicitly or explicitly on ideas from inverse theory - the mathematical framework for relating what we can observe to what we want to know.   I employ seismic tomographic techniques to make detailed models of the Earth's interior, relating sparse data at the surface to complicated 3-D structure at depth.  I am interested in: How well do observations constrain models? What lies hidden beyond the resolution of our data? What are the relative strengths and implications of different inverse theoretical methods (e.g. Bayesian, least squares, Newton's method)?

Selected papers:
- Eilon et al., (2018) An adaptive Bayesian inversion for upper-mantle structure using surface waves and scattered body waves
- Eilon et al. (2016) A Joint Inversion for Shear Velocity and Anisotropy: The Woodlark Rift, Papua New Guinea
- Menke & Eilon (2015) Relationship Between Data Smoothing and the Regularization of Inverse Problems

By stacking error surfaces from individual shear wave splitting measurements we can tightly constrain average splitting for a station. From Eilon et al.. [2014].

Result of a joint body-surface wave inversion at several stations spanning the northwest to north-central US, from the High Lava Plains to the cratonic interior. This plot shows Vs profiles and histograms of posterior model parameters like the crustal thickness and Vp/Vs ratio.

Anisotropy

 

Anisotropy (directional dependence of some physical property, often wave speed) offers a fascinating insight into fabric or structures within the Earth. In turn, this can tell us about flow of rocks over time, the mineralogy at depth, and/or the presence of organised melt. 

Selected papers:
- Eilon et al. (2014) Anisotropy beneath a highly extended continental rift
- Eilon et al. (2016) A Joint Inversion for Shear Velocity and Anisotropy: The Woodlark Rift, Papua New Guinea
- Eilon & Forsyth, (2020) Depth dependent azimuthal anisotropy beneath the Juan de Fuca plate system

Figure from Eilon et al. [2016] showing shear wave splitting through a hexagonally symmetric anisotropic fabric.

Attenuation and anelasticity

 

Attenuation, or loss of seismic energy due to frictional processes as waves propagate, offers a powerful complement to seismic velocity for discriminating the physical state of the Earth's interior. I am interested in making observations of seismic attenuation and harnessing laboratory-derived anelastic scaling relationships to translate those observations into estimates of temperature, composition, melt content, water content, etc. at depth. It's an exciting time to work on this: the experimental rock mechanics community and seismological communities are converging steadily on robust links between what we see in the Earth and what we know from the lab. This collaboration holds real promise for allowing us to not just image, but understand, the Earth beneath our feet. 

Selected papers:
- Soto Castaneda et al., (2021) Teleseismic attenuation, temperature, and melt of the upper mantle in the Alaska subduction zone.
- Eilon & Abers (2017) High seismic attenuation at a mid-ocean ridge reveals the distribution of deep melt
- Dannberg et al. (2017) Grain size evolution in the mantle and its effect on geodynamics, seismic velocities, and attenuation

Attenuated waveforms recorded across the Juan de Fuca plate, coloured by distance from the ridge axis.

 

Schematic figure of melt distribution beneath a mid-ocean ridge, and the accompanying Qs and Vs profiles 'seen' by synthetic seismic rays arriving at seismometers on the seafloor.

 

Useful links

None of these is my work...  I wanted to provide a selection of resources that I have found helpful and that I recommend you check out. 

 

Excellent article on "The Really Big One"  –  Pulitzer Prize winning New Yorker article by Kathryn Shulz on the potential consequences of a M9 earthquake in Cascadia. Aside from a taking a couple of liberties describing the extent of the damage, I think this is the most accurate and best-written 'popular' Earth Science article I've ever read.

USGS latest earthquakes page  –  Nice interactive map with recent large earthquakes worldwide. Filter the data by time and magnitude and select events on the left panel to drill down into the many data products available through this portal, including tectonic summaries,  moment tensors,  waveforms, and much more. 

Temblor earthquake hazard estimator  –  Be forewarned! This fantastic and informative tool helps you understand seismic hazard in your area and provides tools to help you think about retrofitting and earthquake insurance.  If you live in California, this is VERY relevant and deserves your serious attention

For seismologists:

GCMT catalog search  –  Catalog of large (M>5.5ish) globally recorded earthquakes collated by the Global Centroid Moment Tensor project. 

International registry of seismography stations  – Complete registry of operational seismographic stations, maintained by the International Seismological Centre.

IRIS DMC Network List - Aggregated list of all seismic network codes (with description) that have data available through the Data Management Center, including virtual networks that group stations in some relevant way (e.g. GSN, US Transportable Array, OBSIP stations)