About

Jeffrey Park is a Professor of Earth & Planetary Sciences at Yale University and serves as the Director of Graduate Studies in the department. His research focuses on mapping mantle flow associated with plate tectonics using seismic anisotropy, as well as utilizing scattered seismic waves and seismic anisotropy to infer aligned cracks and rock fabrics in the Earth's crust. He has a background in physics, having received his Bachelor of Science Degree from Princeton University in 1979, and earned his Doctorate in Earth Sciences from the University of California, San Diego in 1985. His early interest in earth sciences was sparked by the 1971 earthquake in Sylmar, California, and his subsequent introduction to plate tectonics solidified his commitment to the field. Park has held various offices, including Director of the Yale Institute for Biospheric Studies, Chairman of the Environmental Studies Program at Yale College, and President of the Seismology Section of the American Geophysical Union. His teaching philosophy emphasizes advising students with active curiosity and providing them with projects that foster independence and interest, often leading students to present at scientific meetings within months of research. His background and research contributions are rooted in seismology, geophysics, and earth system science.

Research topics

• Geology
• Oceanography
• Seismology
• Geochemistry
• Mineralogy
• Telecommunications
• Engineering
• Geophysics

Selected publications

• Crustal anisotropy as evidence for hydration of the Martian upper mantle

  Physics of The Earth and Planetary Interiors · 2025-08-09 · 2 citations

  article
  PublisherDOI

• High-resolution mapping of North America suggests numerous low-velocity zones above and below the mantle transition zone

  Tectonophysics · 2025-05-06 · 1 citations

  articleOpen access

  We investigate seismic discontinuities across the middle of Earth's mantle beneath a large seismic array that spans the North American continent. We provide robust constraints on the depth distribution, sharpness, and spatial variation of seismic discontinuities by processing high-resolution Ps-converted seismic waves (~0.5 Hz) through a novel denoising filter called CRISP-RF ( C lean R eceiver function I maging with Sp arse R adon F ilters) . In the upper mantle, above the mantle transition zone (MTZ), we observe a sharp velocity decrease at depths that vary from ~290 km to ~390 km. In the lower mantle, below the MTZ, we observe another sharp velocity decrease at depths that vary from ~800 km to ~1400 km . The lower-mantle discontinuities cluster at a depth of ~940 km, while deeper converters (> 1100 km) are less likely. We evaluate our results against two leading hypotheses: basalt enrichment due to incomplete mixing and dehydration melting in which MTZ water is transported into the upper or the lower mantle, but rarely simultaneously. We conclude that our results are more consistent with a scenario where the complex interplay between composition, volatile content, and subduction history, produces disconnected regions of velocity-inversion interfaces when past convective motions bring hydrated MTZ rock into the hydrophobic upper and lower mantles. • High-resolution mapping reveals sharp velocity drops above and below the mantle transition zone across North America. • Velocity drops rarely occur together above and below the transition zone, suggesting separate origins. • New receiver function filtering technique enhances detection of weak mid-mantle structures previously hidden by noise. • Velocity drops above and below the mantle transition zone show complex spatial and depth distributions.

  PublisherDOI

• Thick Underplating and Buoyancy of the Bermuda Swell

  Geophysical Research Letters · 2025-11-28

  articleOpen accessSenior author

  Abstract Bermuda is an intraplate ocean swell that does not conform to traditional mantle plume theory. Unlike other prominent bathymetric swells, such as Hawaii, it lacks age‐progressive volcanism, a deeply rooted mantle plume, and modern volcanism. High‐frequency receiver‐function imaging of the shallow lithosphere beneath the Bermuda swell reveals two prominent interfaces interpreted as the fossil oceanic Moho and the bottom of an underplated layer. This underplated layer is ∼20 km thick, ∼2x greater than observations at many other intraplate ocean islands. Based on the topography of the Bermuda swell, this layer could be rock that is ∼50 kg/m 3 less dense than the lithospheric mantle it has replaced. We suggest that the Bermuda swell is supported by a ∼20 km thick layer of modified lithospheric mantle, not a hot thermal anomaly from a mantle plume.

  PublisherOA PDFDOI

• High-Resolution Mapping of North America Suggests Numerous Low-Velocity Zones Above and Below the Mantle Transition Zone

  SSRN Electronic Journal · 2025-01-01

  preprintOpen access
  PublisherDOI

• High-resolution Mapping of North America's Mid-Mantle Reflectivity provides Evidence for Dehydration Melting

  2024-08-07

  preprintOpen access

  We investigate seismic discontinuities across the middle of Earth’s mantle beneath a large seismic array that spans the North American continent. We provide robust constraints on the depth distribution, sharpness, and spatial variation of seismic discontinuities by processing high-resolution Ps-converted seismic waves (~0.5 Hz) through a novel denoising filter called CRISP-RF (Clean Receiver function Imaging with Sparse Radon Filters). In the upper mantle, above the mantle transition zone (MTZ), we observe a sharp velocity decrease at depths that vary from ~290 km to ~390 km. In the lower mantle, below the MTZ, we observe another sharp velocity decrease at depths that vary from ~800 km to 1,200 km. The lower-mantle discontinuities cluster at a depth of ~885 km, while deeper converters (> 1,000 km) are less likely. The spatial distribution of these seismic features appears stochastic, but we detect collocated upper-mantle and lower-mantle discontinuities only at 8% of observed locations. We interpret our results with a dehydration melting model, in which MTZ water is transported into either the upper or the lower mantle, but rarely simultaneously, during Earth’s long history of subduction and mantle upwelling.

  PublisherOA PDFDOI

• No globally detectable seismic interfaces within Earth's mantle transition zone: Evidence for basalt enrichment

  Earth and Planetary Science Letters · 2024-06-14 · 8 citations

  articleSenior author
  PublisherDOI

• Identifying vulnerability to human trafficking in Bangladesh: An ecosystem approach using weak‐signal analysis

  Journal of International Development · 2023-08-14 · 6 citations

  articleCorresponding

  Abstract We present an ecosystem approach to analyze open‐source data to identify populations vulnerable to human trafficking and to reveal underlying causal relationships. In the case of Bangladesh, our analysis suggests combinations of indicators that are highly predictive of human trafficking. The traditional narrative that poverty and unemployment are the main drivers for human trafficking may be an oversimplification. We find many areas where vulnerability is highest within lower‐middle to middle‐class societies with (a) moderate levels of income and education, (b) adherence to traditional gender norms of a male‐dominated patriarchal society, and (c) access to an urban center.

  PublisherDOI

• Crustal Anisotropy from the Birefringence of P-to-S Converted Waves: Bias Associated with P-Wave Anisotropy

  Annals of Geophysics · 2023-06-10 · 3 citations

  articleOpen access1st authorCorresponding

  Many researchers have used the birefringence of P‑to‑S converted waves from the Moho discontinuity to constrain the anisotropy of Earth’s crust. However, this practice ignores the substantial influence that anisotropy has on the initial amplitude of the converted wave, which adds to the splitting acquired during its propagation from Moho to the seismometer. We find that large variations in Ps birefringence estimates with back-azimuth occur theoretically in the presence of P‑wave anisotropy, which normally accompanies S‑wave anisotropy. The variations are largest for crustal anisotropy with a tilted axis of symmetry, a geometry that is often neglected in birefringence interpretations, but is commonly found in Earth’s crust. We simulated globally-distributed P‑coda datasets for 36 distinct 4‑layer crustal models with combinations of elliptical shear anisotropy or compressional anisotropy, and also incorporated the higher-order anisotropic Backus parameter C. We tested both horizontal and tilted symmetry-axis geometries and tested the birefringence tradeoff associated with Ps converted phases at the top and bottom of a thin high‑ or low‑velocity basal layer. We computed composite receiver functions (RFs) with harmonic regression over back azimuth, using multipletaper correlation with moveout corrections for the epicentral distances of 471 events, to simulate a realistic data set. We estimate Ps birefringence from the radial and transverse RFs, a strategy that is similar to previous studies. We find that Ps splitting can be a useful indicator of bulk crustal anisotropy only under restricted circumstance, either in media with no compressional anisotropy, or if the symmetry axis is horizontal throughout. In other, more-realistic cases, the inferred fast polarization of Ps birefringence estimated from synthetic RFs tends either to drift with back-azimuth, form weak penalty-function minima, or return splitting times that depend on the thickness of an anisotropic layer, rather than the birefringence accumulated within it.

  PublisherOA PDFDOI

• Detecting Anisotropy from Back-Azimuth Amplitude Dependence of Sp Converted Waves

  2023-02-26

  preprintOpen access1st authorCorresponding

  Many researchers have used S-to-P (Sp) converted waves to detect the Moho discontinuity, the lithosphere-asthenosphere boundary (LAB) and mid-lithospheric discontinuities (MLD). The anisotropy of Earth’s lithosphere is typically constrained with shear-wave birefringence.  Both theory and reflectivity computations, however, argue for a substantial influence of anisotropy on the initial amplitude of the Sp converted wave.  The effects of compressional anisotropy on initial Sp amplitudes are stronger than the effects of shear anisotropy for anisotropy with a tilted axis of symmetry, a geometry that is often neglected in birefringence interpretations.  This Sp behavior is not typically studied, but it has the potential to test the hypothesis that the seismic lithosphere-asthenosphere boundary (LAB) is caused by a transition in anisotropic layering at the base of Earth’s tectonic plates.We develop and apply multiple-taper correlation estimates for Sp receiver functions, applicable to either SV or SH incoming polarization, or for a linear combination of SV and SH. In the context of incoming SV-polarized body waves, e.g., SKS phases, algorithms from multiple-taper Ps RFs can be borrowed to apply moveout corrections before the Fourier transform to target a particular interface depth in the crust or mantle.  With synthetic seismograms, we find that SH “receiver functions” can be computed from incoming SV waves, promising a diagnostic detecting SKS birefringence and to estimate an average splitting signal from a station. The SV and SH waveforms can be “unsplit” in the frequency domain by the estimated average birefringence to reconstruct the S waves that impinge the lithosphere from the deep mantle.  We will report analyses with data from permanent stations of the Global Seismographic Network and the USGS ANSS.

  PublisherDOI

• Global High-Resolution mid-Mantle Imaging with Multiple-Taper SS-Precursor Estimates

  2023-02-26

  preprintOpen accessSenior authorCorresponding

  SS precursor imaging has long been used to detect sharp interfaces within Earth’s mid-Mantle. The topography of the 410- and 660-km discontinuities, the major interfaces in the mantle transition zone (MTZ), can provide valuable insight into the temperature of and material flow within the mantle. Additionally, negative velocity gradients and possible partial melt surrounding the MTZ in some regions provide evidence for a hydrogen-enriched mid-mantle, a feature that may have implications for global water circulation and long-term (~100 Ma) ocean-mass regulation. Here, we apply a novel SS-precursor deconvolution technique based on multiple-taper correlation (MTC). Typical SS-precursor techniques require tightly bandpassed signals (e.g., 0.02-0.1 Hz), limiting both vertical and horizontal resolution. Higher-frequency content allows for the detection of finer structure in and around the MTZ. MTC-based SS-precursor estimates can increase the frequency cutoff to above 0.5 Hz, thereby increasing vertical resolution to under 10 km. We conduct this analysis on a global data set of over 300,000 SS waveforms recorded on the permanent GSN, GEOSCOPE, and GEOFON networks as well as the temporary EarthScope TA and AlpArray. Such a large dataset provides unprecedented bounce-point density, particularly in the North Pacific Ocean. Preliminary results suggest a global average depth of ~409 km and ~665 km for the 410- and 660-km discontinuities respectively. In this work we used time-delays calculated for the 1-D ak135 velocity model. In general, we find moderate agreement with previous low-frequency SS precursor analysis. Additionally, we identify a sharp feature above the MTZ, north of the Hawaiian Islands, that was interpreted previously from an asymmetry in sidelobe amplitudes, suggesting a low-velocity zone with a sharp interface (<10-km thickness), rather than a thick wavespeed gradient. Further results will include corrections for 3-D structure with various mantle tomography models and focus on potential impacts to the solid-Earth water cycle.

  PublisherDOI

Recent grants

• Love-Rayleigh Scattering and Regional Anisotropy in USArray

  NSF · $210k · 2010–2015

Frequent coauthors

• Vadim Levin

  Association for the Development of Earthquake Prediction

  31 shared

• G. Laske

  Scripps Institution of Oceanography

  25 shared

• Heping Sun

  25 shared

• Houze Xu

  Institute of Geodesy and Geophysics

  25 shared

• P. Davis

  University of California, San Diego

  25 shared

• G. Roult

  Université Paris Cité

  25 shared

• Emile A. Okal

  Northwestern University

  25 shared

• Jeroen Tromp

  Princeton University

  25 shared

Awards & honors

• President, Seismology Section of the American Geophysical Un…
• Member of Governing Board, American Institute of Physics (AI…
• Chairman of Executive Committee, Incorporated Research Insti…