Ian Vandevert

Institute of Geophysics and Planetary Physics

Scripps Institution of Oceanography

San Diego, California

Some earthquakes produce lots of damaging high-frequency energy; others of the same magnitude release less. The difference matters: high-frequency radiation is what damages buildings, but we still don’t fully understand why it varies, or what it reveals about the conditions at depth where the rupture happens.

I’m a PhD candidate at Scripps Institution of Oceanography, advised by Peter Shearer and Wenyuan Fan, working on exactly this question. My dissertation develops a metric I call the normalized frequency index (nFI), which measures how much high-frequency energy an earthquake radiates relative to its low-frequency content. Unlike stress-drop estimates, which require fitting a source model to the observed spectrum, nFI is computed directly from the data. That makes it robust across large catalogs and well suited to asking where source properties vary systematically — across fault systems, with depth, between mainshocks and aftershocks. Most recently, I’ve applied it to roughly 775,000 events and 12 million seismograms spanning thirty years of California seismicity, and I’m defending in June 2026.

Before Scripps I did my undergraduate in Earth Science at UC Santa Barbara, where I worked with Toshiro Tanimoto on seismic-noise cross-correlation and Robin Matoza on elastic-wave simulation. Between undergrad and grad school I spent a year as a geotechnical associate in the Bay Area, which is where I first started writing real software.

I’m on the market for postdoc positions starting Fall 2026, with a preference for positions in Europe. I’m interested in anything relating to data science or seismology.

news

Jun 18, 2026	Dissertation defense scheduled for June 2026.
Apr 27, 2026	Attending EGU General Assembly 2026 in Vienna.
Apr 01, 2026	Paper accepted at BSSA: our manuscript introducing the normalized frequency index (nFI) as a robust, model-free measure of earthquake high-frequency radiation.
Dec 09, 2025	Presented at AGU Fall Meeting 2025.
Dec 09, 2024	Received an Outstanding Student Presentation Award at AGU Fall Meeting 2024.

selected publications

BSSA

Using a High- to Low-Frequency Spectral Ratio to Distinguish Variations in Earthquake Source Properties

Ian Vandevert, Peter M. Shearer, and Wenyuan Fan

Bulletin of the Seismological Society of America, 2026

In press

Bib

@article{vandevert2026nfi,
  journal = {Bulletin of the Seismological Society of America},
  title = {Using a High- to Low-Frequency Spectral Ratio to Distinguish Variations in Earthquake Source Properties},
  author = {Vandevert, Ian and Shearer, Peter M. and Fan, Wenyuan},
  year = {2026},
  note = {In press},
}

BSSA
Ridgecrest Aftershock Stress Drops from P- and S-Wave Spectral Decomposition

Ian C. Vandevert, Peter M. Shearer, and Wenyuan Fan

Bulletin of the Seismological Society of America, Nov 2024

Abs DOI Bib HTML

Seismic moment and stress drop are crucial for understanding earthquake rupture processes, but their estimates often have large uncertainties for small earthquakes. Stress drop is typically inferred from an earthquake’s source spectrum based on theoretical models, but poorly constrained path corrections and other modeling assumptions limit the accuracy of stress-drop estimates. Here, we compute stress drops using both P and S waves for the 2019 Ridgecrest earthquake sequence, compare their estimates, and evaluate the associated uncertainties. We use spectral decomposition and apply the analysis to both types of waves for the same set of earthquakes, adjusting some S-wave parameter choices to obtain overall consistency with our P-wave results. Our approach fixes the corner frequency of small calibration earthquakes to reduce scatter in the estimated source parameters of the larger earthquakes. We find that assuming a lower high-frequency fall-off rate for S waves yields more consistent absolute stress-drop estimates between P and S waves. Our stress-drop estimates appear to increase slightly with magnitude for earthquakes with magnitudes >∼3.4. Furthermore, we find that the stress-drop estimates using both types of data exhibit coherent spatial variations. Earthquakes near the Coso geothermal field tend to have lower stress drops, and earthquakes near the M 7.1 hypocenter have higher stress-drop estimates. This spatial pattern is consistently observed in both the P- and S-wave results. We find no strong correlation between our stress-drop estimates and the M 7.1 Ridgecrest earthquake slip distribution, suggesting a heterogeneous stress environment for the Ridgecrest fault system.
@article{vandevert2024ridgecrest, title = {Ridgecrest {{Aftershock Stress Drops}} from {{P}}- and {{S}}-{{Wave Spectral Decomposition}}}, author = {Vandevert, Ian C. and Shearer, Peter M. and Fan, Wenyuan}, year = {2024}, month = nov, journal = {Bulletin of the Seismological Society of America}, issn = {0037-1106}, doi = {10.1785/0120240133}, urldate = {2024-11-27}, copyright = {All rights reserved}, file = {/Users/ivandevert/Zotero/storage/VRQG4LJE/Vandevert et al. - 2024 - Ridgecrest Aftershock Stress Drops from P‐ and S‐W.pdf;/Users/ivandevert/Zotero/storage/C7KAABIE/Ridgecrest-Aftershock-Stress-Drops-from-P-and-S.html} }