My research uses a variety of types of seismic data to understand the structure of the crust and upper mantle, primarily in subduction zones. These results can provide valuable constraints on physical properties of the Earth that are needed to understand the behavior of subduction processes. Current research questions that I am interested in include:
What is the seismic structure of a plate interface in a subduction zone, and how do the structures and compositions along the plate interface influence variations in seismic slip behavior (e.g. megathrust earthquakes, episodic tremor and slow slip, aseismic slip)?
What is the range of magmatic architectures beneath volcanos and how is it related to variations in input? What are the implications for variations in crust production or material transport?
How can we use seismic results to constrain the thermal and compositional state of oceanic lithosphere and asthenosphere outboard of the trench to develop more realistic geodynamic models of subduction?
What are the technical challenges in using seismic data to study subduction zones and volcanoes and how can we address them? How do we most effectively use amphibious seismic data?
More details on ongoing and recent projects can be found below.
Sometimes I also get to see the places I'm studying in person. Here I am at Mt. Rainier.
Variation in average crustal shear velocity beneath Cleveland Volcano.
Constraining Crustal Magmatic Architecture Beneath Volcanoes
Crustal magmatic architecture beneath volcanoes is difficult to seismically image, particularly in the mid- to deep-crust. Receiver functions provide an opportunity to observe low velocity regions likely associated with partial melt, elevated temperatures, or altered material within the crust at these depths without the need for a high-density, large-aperture broadband seismic array. Our results at Cleveland Volcano in the central Aleutian island arc, one of the more active volcanoes in the region, shows evidence for an extensive crustal magma body, likely greater than 10 km deep. This is distinct from a shallower magma body (~ 5-8 km maximum depth) indicated by seismicity and gas measurements. Furthermore, this volcano exhibits different crustal magmatic architecture than Akutan - a volcano in the same arc system - suggesting strong variability in the deeper architecture beneath volcanoes, even in similar tectonic settings.
Example of P-to-S receiver functions calculated from OBS instruments.
Imaging the Plate Interface in the Cascadia Seismogenic Zone
The Cascadia subduction zone has historically produced up to M 9 megathrust earthquakes; however, there is much uncertainty about the structure of the plate interface within the locked zone and its relationship to seismogenic processes. We use receiver functions from OBS stations deployed on the continental shelf off the coast of Washington and a ship-to-shore wide-angle seismic reflection dataset to investigate the seismic structure of the plate interface within the broadly defined locked zone. I am interested in using these results to better understand the scale of heterogeneity along the plate interface and the potential role of fluids and sediments in influencing seismic behavior along the megathrust.
Phase velocity map for Cascadia.
Broad Plate Structures of the Cascadia Subduction Zone
Surface waves from teleseismic earthquakes and ambient noise can help us constrain seismic shear wave velocities related to lithospheric and asthenospheric structure. We create phase velocity maps that cross the coastline, extending over the entire Juan de Fuca plate and Cascadia subduction zone. I am interested in investigating the thermal state of the Juan de Fuca plate as it evolves from the ridge to the trench, the new seismic velocity results in the forearc region spanning the locked zone of the plate interface and the location of episodic tremor and slip, and the seismic velocity structure along the strike of the Cascades volcanic arc in relation to the broader tectonic system.
Comparison of an earthquake recorded prior to and after compliance corrections on an OBS.
Noise Corrections and Analysis on OBS Instruments
The use of ocean bottom seismometers (OBS) can improve our understanding of seismic structure and processes in offshore regions; however, using this data requires careful consideration of the effects of the water column above the instrument. Recent expansion of OBS experiments reinvigorates the need for technique improvement and development. We have successfully used receiver functions calculated from OBS data, a technique that has seen limited success in the past, to image the plate interface in Cascadia. We have also developed a new automated quality control package that streamlines tilt and compliance corrections (stay tuned, will be available soon!). I am interested in further exploring the variability of noise on OBS instruments and further improving the use of existing seismic techniques on OBS data.
Depth to Moho and average crustal Vp/Vs along the Aleutian arc.
Crustal Structure Along the Aleutian Island Arc
The Aleutian island arc is an ideal setting for studying the role of island arcs in continental crust production due to its relative stability and lack of pre-existing volcanism. We used receiver functions to estimate the crustal thickness and average Vp/Vs beneath each of the 13 permanent seismic stations deployed along the Aleutian island arc. These results are compared to the average thickness and composition of continental crust to better understand the process by which island arcs may build continents. We were also able to see evidence of a magma body beneath Akutan volcano due to back azimuthal variation in receiver functions.