Research Interests
Electromagnetic geophysics, marine geophysics, numerical and computational geophysics, hydrocarbon exploration, mid-ocean ridges, subduction zones, volcanoes, mantle dynamics, instrumentation design.
Education
Ph. D., Geophysics, Scripps Institution of Oceanography, University of California San Diego, 2003
B.S., Earth Sciences, University of California San Diego, 1998
Palomar Community College, 1992-1995
Professional Experience
Associate Professor, Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, 2017-present
Visiting Associate Professor, Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, 2017
Associate Professor, Scripps Institution of Oceanography, UC San Diego, 2013-2017
Associate Researcher, Scripps Institution of Oceanography, UC San Diego, 2012-2013
Visiting Scientist, Institute de Physique du Globe de Paris, 2009
Assistant Researcher, Scripps Institution of Oceanography, UC San Diego, 2008-2012
Postdoctoral Researcher, Scripps Institution of Oceanography, UC San Diego, 2004-2008
Primary Code Developer:
MARE2DEM: Modeling with Adaptively Refined Elements for 2D Electromagnetics
Occam1DCSEM – 1D forward and inverse modeling for controlled-source electromagnetic and magnetotelluric geophysical data
Selected Publications
Chesley, Christine; Key, Kerry; Constable, Steven; Behrens, James; MacGregor, Lucy Crustal Cracks and Frozen Flow in Oceanic Lithosphere Inferred From Electrical Anisotropy Journal Article Geochemistry Geophysics Geosystems, 20 (138), pp. 21, 2019. Abstract | Links @article{Chesley:2019fv,
title = {Crustal Cracks and Frozen Flow in Oceanic Lithosphere Inferred From Electrical Anisotropy},
author = {Christine Chesley and Kerry Key and Steven Constable and James Behrens and Lucy MacGregor},
url = {http://emlab.ldeo.columbia.edu/wp-content/uploads/2019/12/Chesley_et_al-2019-Geochemistry_Geophysics_Geosystems.pdf},
year = {2019},
date = {2019-12-01},
journal = {Geochemistry Geophysics Geosystems},
volume = {20},
number = {138},
pages = {21},
abstract = {Geophysical observations of anisotropy in oceanic lithosphere offer insight into the formation and evolution of tectonic plates. Seismic anisotropy is well studied but electrical anisotropy remains poorly understood, especially in the crust and uppermost mantle. Here we characterize electrical anisotropy in 33 Ma Pacific lithosphere using controlled‐source electromagnetic data that are highly sensitive to lithospheric azimuthal anisotropy. Our data reveal that the crust is ∼18–36 times more conductive in the paleo mid‐ocean ridge direction than the perpendicular paleo‐spreading direction, while in the uppermost mantle conductivity is ∼29 times higher in the paleo‐spreading direction. We propose that the crustal anisotropy results from subvertical porosity created by ridge‐parallel normal faulting during extension of the young crust and thermal stress‐driven cracking from cooling of mature crust. The magnitude of uppermost mantle anisotropy is consistent with recent experimental results showing strong electrical anisotropy in sheared olivine, suggesting its paleo‐spreading orientation results from sub‐Moho mantle shearing during plate formation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Geophysical observations of anisotropy in oceanic lithosphere offer insight into the formation and evolution of tectonic plates. Seismic anisotropy is well studied but electrical anisotropy remains poorly understood, especially in the crust and uppermost mantle. Here we characterize electrical anisotropy in 33 Ma Pacific lithosphere using controlled‐source electromagnetic data that are highly sensitive to lithospheric azimuthal anisotropy. Our data reveal that the crust is ∼18–36 times more conductive in the paleo mid‐ocean ridge direction than the perpendicular paleo‐spreading direction, while in the uppermost mantle conductivity is ∼29 times higher in the paleo‐spreading direction. We propose that the crustal anisotropy results from subvertical porosity created by ridge‐parallel normal faulting during extension of the young crust and thermal stress‐driven cracking from cooling of mature crust. The magnitude of uppermost mantle anisotropy is consistent with recent experimental results showing strong electrical anisotropy in sheared olivine, suggesting its paleo‐spreading orientation results from sub‐Moho mantle shearing during plate formation. |
Gustafson, Chloe; Key, Kerry; Evans, Rob L Aquifer systems extending far offshore on the U.S. Atlantic margin Journal Article Scientific Reports, 9 (1), 2019. Abstract | Links @article{freshwaterSR,
title = {Aquifer systems extending far offshore on the U.S. Atlantic margin},
author = {Chloe Gustafson and Kerry Key and Rob L Evans },
url = {https://doi.org/10.1038/s41598-019-44611-7},
doi = {10.1038/s41598-019-44611-7},
year = {2019},
date = {2019-06-19},
journal = {Scientific Reports},
volume = {9},
number = {1},
abstract = {Low-salinity submarine groundwater contained within continental shelves is a global phenomenon. Mechanisms for emplacing offshore groundwater include glacial processes that drove water into exposed continental shelves during sea-level low stands and active connections to onshore hydrologic systems. While low-salinity groundwater is thought to be abundant, its distribution and volume worldwide is poorly understood due to the limited number of observations. Here we image laterally continuous aquifers extending 90 km offshore New Jersey and Martha’s Vineyard, Massachusetts, on the U.S. Atlantic margin using new shallow water electromagnetic geophysical methods. Our data provide more continuous constraints on offshore groundwater than previous models and present evidence for a connection between the modern onshore hydrologic system and offshore aquifers. We identify clinoforms as a previously unknown structural control on the lateral extent of low-salinity groundwater and potentially a control on where low-salinity water rises into the seafloor. Our data suggest a continuous submarine aquifer system spans at least 350 km of the U.S. Atlantic coast and contains about 2800 km3 of low-salinity groundwater. Our findings can be used to improve models of past glacial, eustatic, tectonic, and geomorphic processes on continental shelves and provide insight into shelf geochemistry, biogeochemical cycles, and the deep biosphere.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Low-salinity submarine groundwater contained within continental shelves is a global phenomenon. Mechanisms for emplacing offshore groundwater include glacial processes that drove water into exposed continental shelves during sea-level low stands and active connections to onshore hydrologic systems. While low-salinity groundwater is thought to be abundant, its distribution and volume worldwide is poorly understood due to the limited number of observations. Here we image laterally continuous aquifers extending 90 km offshore New Jersey and Martha’s Vineyard, Massachusetts, on the U.S. Atlantic margin using new shallow water electromagnetic geophysical methods. Our data provide more continuous constraints on offshore groundwater than previous models and present evidence for a connection between the modern onshore hydrologic system and offshore aquifers. We identify clinoforms as a previously unknown structural control on the lateral extent of low-salinity groundwater and potentially a control on where low-salinity water rises into the seafloor. Our data suggest a continuous submarine aquifer system spans at least 350 km of the U.S. Atlantic coast and contains about 2800 km3 of low-salinity groundwater. Our findings can be used to improve models of past glacial, eustatic, tectonic, and geomorphic processes on continental shelves and provide insight into shelf geochemistry, biogeochemical cycles, and the deep biosphere. |
Blatter, Daniel; Key, Kerry; Ray, Anandaroop; Gustafson, Chloe; Evans, Rob Bayesian Joint Inversion of Controlled Source Electromagnetic and Magnetotelluric Data to Image Freshwater Aquifer Offshore New Jersey Journal Article Geophysical Journal International, 2019, ISSN: 0956-540X. Abstract | Links @article{10.1093/gji/ggz253,
title = {Bayesian Joint Inversion of Controlled Source Electromagnetic and Magnetotelluric Data to Image Freshwater Aquifer Offshore New Jersey},
author = {Daniel Blatter and Kerry Key and Anandaroop Ray and Chloe Gustafson and Rob Evans},
url = {http://emlab.ldeo.columbia.edu/wp-content/uploads/2019/12/6FA32540-AE06-4DF8-93A2-E5FA1D3AAEC8.pdf},
issn = {0956-540X},
year = {2019},
date = {2019-01-01},
journal = {Geophysical Journal International},
abstract = {Joint inversion of multiple electromagnetic data sets, such as controlled source electromagnetic and magnetotelluric data, has the potential to significantly reduce uncertainty in the inverted electrical resistivity when the two data sets contain complementary information about the subsurface. However, evaluating quantitatively the model uncertainty reduction is made difficult by the fact that conventional inversion methods – using gradients and model regularization – typically produce just one model, with no associated estimate of model parameter uncertainty. Bayesian inverse methods can provide quantitative estimates of inverted model parameter uncertainty by generating an ensemble of models, sampled proportional to data fit. The resulting posterior distribution represents a combination of a priori assumptions about the model parameters and information contained in field data. Bayesian inversion is therefore able to quantify the impact of jointly inverting multiple data sets by using the statistical information contained in the posterior distribution. We illustrate, for synthetic data generated from a simple 1D model, the shape of parameter space compatible with controlled source electromagnetic and magnetotelluric data, separately and jointly. We also demonstrate that when data sets contain complementary information about the model, the region of parameter space compatible with the joint data set is less than or equal to the intersection of the regions compatible with the individual data sets. We adapt a trans-dimensional Markov chain Monte Carlo algorithm for jointly inverting multiple electromagnetic data sets for 1D Earth models and apply it to surface-towed controlled source electromagnetic and magnetotelluric data collected offshore New Jersey, USA, to evaluate the extent of a low salinity aquifer within the continental shelf. Our inversion results identify a region of high resistivity of varying depth and thickness in the upper 500 m of the continental shelf, corroborating results from a previous study that used regularized, gradient-based inversion methods. We evaluate the joint model parameter uncertainty in comparison to the uncertainty obtained from the individual data sets and demonstrate quantitatively that joint inversion offers reduced uncertainty. In addition, we show how the Bayesian model ensemble can subsequently be used to derive uncertainty estimates of pore water salinity within the low salinity aquifer.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Joint inversion of multiple electromagnetic data sets, such as controlled source electromagnetic and magnetotelluric data, has the potential to significantly reduce uncertainty in the inverted electrical resistivity when the two data sets contain complementary information about the subsurface. However, evaluating quantitatively the model uncertainty reduction is made difficult by the fact that conventional inversion methods – using gradients and model regularization – typically produce just one model, with no associated estimate of model parameter uncertainty. Bayesian inverse methods can provide quantitative estimates of inverted model parameter uncertainty by generating an ensemble of models, sampled proportional to data fit. The resulting posterior distribution represents a combination of a priori assumptions about the model parameters and information contained in field data. Bayesian inversion is therefore able to quantify the impact of jointly inverting multiple data sets by using the statistical information contained in the posterior distribution. We illustrate, for synthetic data generated from a simple 1D model, the shape of parameter space compatible with controlled source electromagnetic and magnetotelluric data, separately and jointly. We also demonstrate that when data sets contain complementary information about the model, the region of parameter space compatible with the joint data set is less than or equal to the intersection of the regions compatible with the individual data sets. We adapt a trans-dimensional Markov chain Monte Carlo algorithm for jointly inverting multiple electromagnetic data sets for 1D Earth models and apply it to surface-towed controlled source electromagnetic and magnetotelluric data collected offshore New Jersey, USA, to evaluate the extent of a low salinity aquifer within the continental shelf. Our inversion results identify a region of high resistivity of varying depth and thickness in the upper 500 m of the continental shelf, corroborating results from a previous study that used regularized, gradient-based inversion methods. We evaluate the joint model parameter uncertainty in comparison to the uncertainty obtained from the individual data sets and demonstrate quantitatively that joint inversion offers reduced uncertainty. In addition, we show how the Bayesian model ensemble can subsequently be used to derive uncertainty estimates of pore water salinity within the low salinity aquifer. |
Key, Kerry MARE2DEM: a 2-D inversion code for controlled-source electromagnetic and magnetotelluric data Journal Article Geophysical Journal International, 207 (1), pp. 571–588, 2016. Links @article{Key:2016eq,
title = {MARE2DEM: a 2-D inversion code for controlled-source electromagnetic and magnetotelluric data},
author = {Kerry Key},
url = {http://emlab.ldeo.columbia.edu/wp-content/uploads/2018/02/GJI-Key-2016.pdf},
year = {2016},
date = {2016-01-01},
journal = {Geophysical Journal International},
volume = {207},
number = {1},
pages = {571--588},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
Naif, Samer; Key, Kerry; Constable, Steven; Evans, Rob L Porosity and fluid budget of a water-rich megathrust revealed with electromagnetic data at the Middle America Trench Journal Article Geochemistry Geophysics Geosystems, 17 (11), pp. 4495–4516, 2016. Links @article{Naif:2016ea,
title = {Porosity and fluid budget of a water-rich megathrust revealed with electromagnetic data at the Middle America Trench},
author = {Samer Naif and Kerry Key and Steven Constable and Rob L Evans},
url = {http://emlab.ldeo.columbia.edu/wp-content/uploads/2018/01/G3-Naif-2016.pdf},
year = {2016},
date = {2016-01-01},
journal = {Geochemistry Geophysics Geosystems},
volume = {17},
number = {11},
pages = {4495--4516},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
Key, Kerry; Constable, Steven; Liu, Lijun; Pommier, Anne Electrical image of passive mantle upwelling beneath the northern East Pacific Rise Journal Article Nature, 495 (7442), pp. 499–502, 2013. Links @article{Key:2013gl,
title = {Electrical image of passive mantle upwelling beneath the northern East Pacific Rise},
author = {Kerry Key and Steven Constable and Lijun Liu and Anne Pommier},
url = {http://emlab.ldeo.columbia.edu/wp-content/uploads/2018/01/Nature-2013-Key.pdf},
year = {2013},
date = {2013-03-01},
journal = {Nature},
volume = {495},
number = {7442},
pages = {499--502},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
Naif, Samer; Key, Kerry; Constable, Steven; Evans, Rob L Melt-rich channel observed at the lithosphere-asthenosphere boundary Journal Article Nature, 495 (7441), pp. 356–359, 2013. Links @article{Naif:2013gh,
title = {Melt-rich channel observed at the lithosphere-asthenosphere boundary},
author = {Samer Naif and Kerry Key and Steven Constable and Rob L Evans},
url = {http://emlab.ldeo.columbia.edu/wp-content/uploads/2018/01/Nature-2013-Naif.pdf},
year = {2013},
date = {2013-03-01},
journal = {Nature},
volume = {495},
number = {7441},
pages = {356--359},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|