Join the lab · Ph.D. & postdoc

Read the seismograms of three worlds

You would work with seismic data from Earth, from NASA's InSight lander on Mars and from the Apollo network on the Moon, and build the Bayesian, waveform-modeling and machine-learning tools needed to read them. Questions run from the core–mantle boundary to landmines a few centimeters underground.

How to reach out Ph.D. program facts Postdocs

Schematic seismograms (not real data): Earth's global networks record many stations per event; Mars has one seismometer; Apollo records ring with long scattered coda.

Research you could join

Questions you could work on

Each question comes from the group's recent papers and lab write-ups. Follow the links to the research overview, the topic-filtered publication list, or the plain-language write-up.

Mars

What sits at the bottom of Mars's mantle?

InSight's single seismometer recorded the first waves observed to cross the Martian core. Whether the deepest reflector is the core itself or a molten silicate layer above it changes the inferred core radius (≈1830 km versus ≈1650 km) and the story of Mars's lost dynamo. The group is now re-examining phase identifications across the InSight catalog under a NASA Mars Data Analysis Program award.

Irving et al., PNAS 2023 · Samuel et al., Nature 2023 · Samuel et al., Icarus 2026

Research Papers Write-up

Deep Earth

What are the giant slow patches on the core–mantle boundary made of?

Beneath Hawai‘i lies a mega-ultralow-velocity zone roughly 900 km across. Ordering thousands of core-diffracted waveforms with the Sequencer, then matching P- and S-wave postcursors with 3-D spectral-element simulations points to solid, iron-rich rock rather than melt, and suggests ULVZs may not be a single class of object.

Kim et al., Science 2020 · Kim et al., Science Advances 2026

Research Papers Write-up

Moon

How thick is the Moon's crust, and what will the next seismometers find?

Converted waves pulled out of Apollo records, using polarization methods first refined on Mars, give crustal thickness beneath three Apollo stations and a global average of 29–47 km, with predictions for the Farside Seismic Suite at Schrödinger basin. Analog fieldwork asks how to image the lunar subsurface within a real mission's budget.

Kim et al., GRL 2025 · Wang et al., JGR Planets, GRL & Earth and Space Science 2025

Research Papers Write-up

Earthquakes

Why do some eastern U.S. earthquakes produce so few aftershocks?

Seismometers installed the day after the 2017 M4.2 Delaware earthquake caught 108 aftershocks, more than ten times the regional catalog, on a previously unmapped fault. Productivity was still far below expectations, and neither high stress drop nor fault orientation explains it. That matters for aftershock forecasts across the central and eastern U.S.

Pearson, Lekić & Wagner, Seismological Research Letters 2026

Research Papers Write-up

Methods

What should you report when an inversion returns a million models?

Bayesian samplers return populations of models, and their average can be a model the data reject. The group develops transdimensional inversions, k-medoids summaries that show real sampled models along with their misfit, and GPU samplers that reach a billion parameters on a single consumer GPU.

Mills, Rudolph & Lekić, JGR: Machine Learning and Computation 2025

Research Papers Write-up

Humanitarian

Can a drone find a landmine?

On the order of a hundred million landmines and pieces of unexploded ordnance remain in the ground. The group's TetraMag gradiometer treats the "error" from a finite-size instrument as information about how deep a small target lies, a step toward magnetometers bolted rigidly to drones.

Myers, Lathrop & Lekić, Geophysics 2025 · U.S. Patent 12,461,273

Research Papers Write-up

Ice & Icy Worlds

What can seismology say about ice shelves and ocean worlds?

On Antarctica's Ross Ice Shelf, rate-and-state friction laws predict seismicity rates on ice rifts. On Europa, fundamental-mode surface waves could measure the thickness of the ice shell above its ocean. Both problems apply the same physics to ice on Earth and beyond.

Udell-Lopez, Huang & Lekić, EPSL 2026 · Maguire et al., Icarus 2021

Research Papers

Lithosphere

What do converted waves reveal under sediments and continents?

Receiver functions map layering in the crust and upper mantle, but sediment reverberations and joint-inversion choices can create structure that isn't there. Group work corrected for sediments along the Atlantic Coastal Plain and showed when low-velocity zones are spurious. The same tools now probe the Martian crust away from InSight's landing site.

Cunningham & Lekić, GJI 2019, BSSA 2020 · Gao, Cunningham & Lekić, GJI 2019

Research Papers Write-up

Your question

Have a different idea?

Some of the group's recent work sits where two threads meet, such as a polarization method built for Mars and then turned on Apollo data. If your question needs seismic data, inverse methods or a new instrument, describe it in your email.

How to reach out

Training

What you'll learn

These are the tools the group's papers actually use. Each tile names where the skill appears in published or ongoing work.

Seismic imaging & tomography

Transdimensional P-wave tomography of North America, the first tomographic model of the uppermost inner core, and the community 3-D Reference Earth Model (REM-3D).

Bayesian & transdimensional inversion

Receiver-function deconvolution, surface-wave, gravity and joint gravity–magnetic inversions with explicit uncertainty. Lekić teaches the graduate course on inverse theory.

Full-waveform & numerical modeling

3-D spectral-element simulations of core-diffracted waves beneath Hawai‘i. Lekić's own Ph.D. developed spectral-element-based waveform tomography of the upper mantle.

Machine learning

The Sequencer manifold-learning algorithm applied to seismograms (Science, 2020), cluster analysis of tomographic models and model ensembles, and machine learning for landmine detection.

HPC & GPU computing

Vendor-neutral GPU code that runs one source tree on NVIDIA, AMD and Intel hardware and samples a billion parameters, plus large wavefield simulations.

Planetary mission data

InSight marsquake records, the Apollo seismic network and GRAIL gravity. The group was part of the InSight analyses that measured Mars's crust, mantle and core.

Signal processing & array methods

Frequency-dependent polarization analysis, source-array processing of marsquakes, template-matching detection and compressive-sensing acquisition design.

Field & near-surface geophysics

A rapid aftershock deployment after the 2017 Delaware earthquake, and multi-sensor ground and drone surveys for buried ordnance with lidar positioning.

Graduate courses Lekić teaches

GEOL 657 Seismology & Seismic Wave Propagation
GEOL 647 Observational Geophysics
GEOL 789E Inverse Problem Theory
GEOL 789M Machine Learning in Geoscience
GEOL 789G Advanced Geophysics Seminar

Source: Lekić CV (Aug. 2026), courses taught 2012–2026.

Outcomes

Where our alumni go

Former postdocs and graduate students now hold faculty posts, research positions at national labs and observatories, and roles in government and industry.

Current positions · postdoc, Ph.D. and M.S. alumni

Undergraduate researchers went on to

All undergraduate researchers and interns

Sources: lab Former Members page, Lekić CV (Aug. 2026) and alumni's institutional profiles, checked 4 Oct 2026.

UMD Geological, Environmental & Planetary Sciences

The Ph.D. program

Key facts from the department's graduate pages and the 2026–2027 Graduate Catalog. Lekić is the department's Director of Graduate Studies.

Funding: With satisfactory progress, admitted Ph.D. students receive four years of full support (two for the M.S.) as a teaching or research assistantship. Assistantships include a 12-month stipend, tuition remission and medical coverage. They do not cover mandatory fees, currently about $820 per semester.
Deadline: January 8, 2027 for Fall 2027 entry (domestic and international applicants). Spring 2027 entry: October 30, 2026 (domestic) or September 30, 2026 (international).
Application: Statement of purpose answering the department's four program-specific questions, transcripts (unofficial copies are fine at the application stage), three letters of recommendation, and TOEFL/IELTS/PTE scores for international applicants where required.
GRE: The GRE is not listed among the application requirements on the department page or in the Graduate Catalog.
Background: The program admits applicants with degrees in geology, physics, mathematics, chemistry, biology, engineering or related sciences. The geophysics track welcomes physics and astronomy majors with little or no geology background. Expected coursework: at least a year of calculus and a semester of physics.
Timeline: A Ph.D. typically takes four to five years from a bachelor's degree, or three to four after an M.S. It includes coursework, a qualifying exam and proposal defense, and a dissertation defense.
Setting: The department has about 35 graduate students. Regional collaborators include NASA Goddard Space Flight Center, the USGS, the Carnegie Earth and Planets Laboratory, the Smithsonian and NIST, and ESSIC is a joint center with NASA Goddard.

Prospective students

How to reach out

A short, specific email is the best start. Here is what helps.

Which question draws you, and why. Name one or two of the directions above, or a recent paper, and say what you would want to try next.
What you bring. Coursework in physics and mathematics, programming (Python, MATLAB, Julia, C/Fortran, GPU), research or field experience. Concrete beats comprehensive.
A CV and unofficial transcript as attachments.
Your timeline. Which entry term you are applying for, and any fellowships you hold or are applying to.

Contact

Lekić's email address is on the lab's contact page.

Lab contact page UMD directory

Bring a fellowship?

External fellowships add flexibility. Recent group members have held the DOE Computational Science Graduate Fellowship, the NSF Graduate Research Fellowship and the DoD NDSEG Fellowship. Lekić himself held an NSF Graduate Research Fellowship.

Postdoctoral researchers

Postdocs

Postdocs typically join through a grant-funded project or bring an independent fellowship. The fellowships below are commonly used to join a host lab.

NSF · Earth Sciences (EAR)

EAR Postdoctoral Fellowship

Up to two years of support, taken to an eligible host institution. NSF encourages applicants to move beyond their doctoral institution. Lekić was himself an NSF Postdoctoral Fellow at Brown (2010–2011).

nsf.gov NASA · administered by ORAU

NASA Postdoctoral Program

Fellowships hosted at NASA centers, including Goddard Space Flight Center in Greenbelt, Maryland. The program site listed its November 2026 cycle as open on 4 Oct 2026.

npp.orau.org UMD · NASA Goddard

ESSIC

The Earth System Science Interdisciplinary Center is a joint venture of UMD's Geology, AOSC and Geographical Sciences departments with the Earth Sciences Directorate at NASA Goddard. Check its current research positions.

essic.umd.edu European Commission

MSCA Global Postdoctoral Fellowships

For nationals or long-term residents of EU Member States or Horizon Europe Associated Countries: 1–2 years at a host in a non-associated third country such as the U.S., then a one-year return phase.

ec.europa.eu

Grant-funded positions. The group's current postdoc leads its NASA Mars Data Analysis Program project (2024–2027), applying source-array methods to marsquake waveforms. To ask about upcoming openings or to plan a fellowship application together, use the lab contact page. It helps to include a CV, two representative papers and a one-paragraph research idea.

FAQ

Frequently asked questions

Do I need an undergraduate degree in geology?

No. The Graduate Catalog says the geophysics program welcomes students with undergraduate degrees in physics or astronomy and little or no geology background. Expected coursework is at least a year of calculus and a semester of physics. Several of the group's projects are mainly computational.

How is the Ph.D. funded?

Admitted Ph.D. students receive four years of full support with satisfactory progress, as a teaching or research assistantship. That includes a 12-month stipend, tuition remission and medical coverage, but not mandatory fees (about $820 per semester). See program facts.

Is the GRE required?

As of 4 October 2026, the GRE is not listed among the application requirements on the department's graduate page or in the Graduate Catalog. Confirm with the Graduate Program Coordinator (grad-sec@umd.edu) before you apply.

When is the deadline?

January 8, 2027 for Fall 2027 entry, for both domestic and international applicants. It helps to get in touch in the fall, well before the deadline.

Can I be co-advised?

Yes, and it is common in this group. Recent students were co-advised with Daniel Lathrop (physics and landmine detection), Laurent Montési (planetary gravity), Nicholas Schmerr (planetary seismology) and Jill Mikucki at the University of Tennessee (astrobiology). Earlier students were co-advised with Karen Prestegaard (river seismology).

Will I do fieldwork?

That depends on the project. Students in the group have installed seismometers the day after an earthquake (Delaware, 2017) and tested a tetrahedral magnetic gradiometer over a buried-target test bed at the Paint Branch Turfgrass Research Facility in College Park. Planetary-analog seismic surveys with collaborators have run at Kilbourne Hole (New Mexico), the San Francisco Volcanic Field (Arizona) and Lava Beds National Monument (California). Many projects are entirely computational.

Is there a master's option?

Yes. The M.S. normally takes two to three years, includes a research thesis, and comes with two years of assistantship support for students making satisfactory progress. Group M.S. alumni work at the USGS, among other places (see alumni).

Do you have open postdoc positions?

Openings depend on funding. Reach out through the lab contact page, and consider the fellowship routes. Fellowship proposals are strongest when planned together well before the deadline.