Research Interests
My research interests can be broadly defined as tectonics and seismology. My career started as a geology student, and my interest in understanding the Earth has brought me along a meandering path through seismology and mantle dynamics and currently include a study looking at coupled tectonic and surface processes in extensional settings.
Tectonic Influences on Surface Dynamics
At New Mexico Tech, I became involved in a study that uses a numerical landscape evolution model to better understand the interplay between tectonics and sedimentation in the Western United States. As part of this, my interests have expanded towards topics of transport and sedimentation processes in response to tectonic uplift/subsidence and climatic changes through time. Ultimately this will help to inform our long-term understanding of groundwater in such regions.
Mantle Structure beneath Continental Rifts
As an NSF postdoctoral fellow affiliated with Penn State and University of Rhode Island, I researched the upper mantle and the mantle transition zone beneath the continents of Antarctica and Africa.
In Antarctica, I used seismic receiver functions to estimate mantle transition zone thickness to see whether upper mantle thermal anomalies beneath the West Antarctica Rift System continue deeper into the mantle transition zone. I found several regions beneath West Antarctica and the Transantarctic Mountains where the mantle transition zone is thinned, suggesting that it is hotter than average. Through this research, I also saw indications for a low-velocity region directly above the transition zone, which could indicate a layer of dense partial melts present above a hydrated transition zone.
In Africa, I inverted for Earth structure in this region using a 3-D finite-difference waveform tomography method applied to long-period (>200 seconds) signals obtained from ambient seismic noise. The results from this research better resolves velocity anomalies in the African upper mantle that were not well-defined in past studies, due to the sparse distribution of broadband seismometers in many regions of Africa. This paper is published in Geochemistry, Geophysics, Geosystems (Emry et al., 2019) and the final models are available from the IRIS Earth Model Collaboration (http://ds.iris.edu/ds/products/emc-africaantemry-etal2018/).
I have an ongoing interest in the tectonics of Africa and Antarctica, and I am currently ramping up new projects. Check back for updates!
Subduction Zone Tectonics
As a Ph.D. student at Washington University in St. Louis, I researched shallow seismicity in subduction zone settings. I focused on the Mariana subduction zone, a place where no great earthquakes have occurred during our instrumental records and has been considered to be incapable of producing such devastating events. By exploring patterns of shallow seismicity along sections of the plate interface, I concluded that the seismogenic portion of the plate interface extends to depths of 55-60 km. This is important, because it was previously assumed that this region could not produce a large earthquake due to an anomalously narrow seismogenic plate interface. This work, which is published in Geochemistry, Geophysics, Geosystems (Emry et al., 2011) suggests that a different process must be limiting the seismic potential here.
I also examined the seismic potential of the Mariana subduction zone by investigating earthquakes within the Pacific plate seaward of the subduction zone trench, in order to understand the stress distribution within a bending plate and how it may be related to strong plate interface coupling. Through a combination of earthquake waveform modeling and plate flexure, I concluded that the stress distribution within the Pacific plate at Southern Mariana is more strongly compressional than in the north, in concordance with ideas that the plate interface might be more strongly coupled in the south. This work was published in Journal of Geophysical Research (Emry et al., 2014).
Faulting within bending oceanic plates prior to subduction is thought to create pathways by which water can enter and hydrate the incoming plate mantle, allowing for a non-trivial amount of water to be carried into the subduction zone system and possibly deeper in the Earth. I further researched intraplate earthquakes within the incoming plate throughout northern and western Pacific subduction zones and found that extensional faulting occurs to ~10-15 km within the plate mantle, suggesting that a significant amount of water might be incorporated into the downgoing slab. This work was published in Earth and Planetary Science Letters (Emry and Wiens, 2015).