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Prudens quaestio dimidium scientiae - Bacon
My research explores how seismic waves can help us understand the Earth’s structure and its dynamic processes, from the shallow crust to the deep mantle. Seismic waves carry invaluable information about Earth's interior, offering insights into both its history and ongoing processes. I work with broadband seismic data and use a mix of techniques like array processing, receiver functions, shear-wave splitting, and forward modeling to tease out signals that reveal what’s happening below our feet. I’m especially interested in subduction zones, how slabs behave as they sink into the mantle and how they interact with surrounding flow. I’ve previously used seismic methods to map sediment thickness, which can help with critical mineral exploration. At the heart of it, I’m drawn to questions that link seismic observations to big-picture Earth dynamics, and I care deeply about how we communicate those insights-visually, clearly, and in ways that make science more accessible.
Research themes
Subduction zones and slab dynamics
I study how tectonic plates bend, sink, and interact with the surrounding mantle as they descend into Earth’s interior. A key question guiding my work is what causes some slabs to stagnate in the upper mantle while others penetrate deeper toward the core-mantle boundary? The figure below from Goes et al. (2017) encapsulates this.
My current work uses array seismology (explanation by Dan Frost) to track the geometry and depth of subducting slabs and relate them to mantle flow. In parallel, I have shown that near-surface crustal structure can bias array-based measurements by mislocating scatterers by several hundred kilometres. This highlights the importance of correcting for receiver-side effects to ensure that inferences about slab geometry and mantle heterogeneity are robust. Because large-aperture arrays are increasingly used for global studies, this work has broad implications for all deep Earth array-based investigations.
In the past (Agrawal et al., 2020), I've examined deformation within the Nazca slab beneath South America to understand how subducted plates respond to changing stress and rheology with depth, using seismic anisotropy as a proxy. These studies aim to connect deep Earth structure with the large-scale circulation that drives plate tectonics.
Mapping sedimentary basins with passive seismic methods
I'm interested in using passive seismic techniques to estimate sediment thickness and physical properties. Sediment-hosted deposits supply much of the world’s copper and cobalt, and about 14% of the U.S. GDP comes from mining. Yet many basins remain poorly mapped because active seismic surveys and drilling are expensive over large areas. Passive-seismic deployments are relatively low-cost and portable, providing a practical alternative for initial surveys.
Using seismic stations in South Australia, which cover regions with diverse sediment distributions, we developed a method to determine the basement depth based on the arrival time of the P-converted-to-S phase generated at the boundary between the crustal basement and the sedimentary strata above (Agrawal et al., 2022). We expanded this method to all of Australia, helping identify buried basins that may host critical minerals while also improving seismic hazard assessments by refining site-response models (Marignier et al., 2024).
Crustal architecture using receiver functions
Understanding crustal thickness and structure is important for both tectonic and hazard studies. A current project uses receiver functions to image the crust beneath South Carolina, a region that experienced the 2021 Elgin earthquake swarm and lies within the sedimentary Atlantic Coastal Plain. The goal is to understand how crustal architecture influences the distribution of seismicity in the southeastern United States.
Earlier work in a sediment-overburdened region showed that combining passive seismic data with geological information can reveal deep crustal boundaries even where traditional imaging methods struggle. To overcome this, we implemented a filter to minimize the impact of reverberations caused by the sedimentary rocks, allowing us to focus on signals originating from the crust-mantle boundary (Agrawal et al., 2023).
Intraplate Earthquakes and Great Artesian Basin springs - a tryst
The Australian continent, being void of plate boundaries, is often perceived as seismically quiescent. However, earthquakes of moderate magnitude (M6+) occur on the continent around once per decade. Within Australia the distribution of intra-plate seismicity is non-uniform, but instead tends to concentrate along certain weak zones of increased activity. One such region is the eastern margin of the Gawler Craton in South Australia, one of the oldest building blocks of the continent.
Recent deployment of new seismic arrays has greatly improved data coverage, revealing previously undetected local earthquakes. These earthquakes align with the edge of the Gawler Craton and show a strong correlation with mound springs, which are discharge points for groundwater from the Great Artesian Basin. The seismic activity is likely caused by changes in fault permeability, leading to accumulated stress and hydrofracturing-induced earthquakes (Agrawal et al., 2024).
PhD thesis titled "Seismicity and structure of the eastern Gawler Craton and Lake Eyre region" can be accessed here.
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