Fred Pollitz is a research geophysicist with the U.S. Geological Survey. He received his Ph.D in Geophysics (long-period seismology) from Princeton University in 1989, advised by Tony Dahlen.
As a postdoctoral researcher he switched focus to crustal deformation studies, motivated initially through collaboration with Dr. Selwyn Sacks at the Carnegie Institution of Washington. With the USGS since 2000, he has continued to work on problems related to crustal deformation and long-period seismology.
Education:
B.Sc. in Mathematics, Massachusetts Institute of Technology, Cambridge, MA USA (1984)
B.Sc. in Geophysics, Massachusetts Institute of Technology, Cambridge, MA USA (1984)
Ph.D. in Geophysics, Princeton University, Princeton, NJ USA (1989)
Professional Experience:
1997 to 2000: Postdoctoral Researcher, University of California, Davis
1995 to 1997: Isaac Newton Trust Postdoctoral Fellow, University of Cambridge, England
1993 to 1995: Alexander von Humboldt Postdoctoral Fellow, Geophysical Institute, Karlsruhe, Germany
1992 to 1993: CNRS Research Associate, Laboratoire de Sismologie, Institut de Physique du Globe, Paris
1989 to 1991: Postdoctoral Fellow, Department of Terrestrial Magnetism, Carnegie Institution of Washington
Honors and Offices:
2010 - First author of two of the 20 most cited `earthquake’ papers of the period
2000-2010
(http://www.sciencewatch.com/ana/st/earthquakes2/papers10yr/)
2002 - 2013 - Associate Editor, Bulletin of the Seismological Society of America
1998 - 2001 - Associate Editor, Journal of Geophysical Research
Science and Products
Geodetic deformation model results and corrections for use in U.S. National Seismic Hazard Model 2023
This page houses model results used in the U.S. National Seismic Hazard Model, 2023. We include results from four geodetic deformation models (Pollitz, Zeng, Shen, Evans), post-seismic relaxation ("ghost transient") calculation (Hearn), and creep calculation (Johnson/Murray). Geologic deformation model results are available in Hatem et al. (2022a).
An overview of all model procedures and comparis
Earthquake geology inputs for the U.S. National Seismic Hazard Model (NSHM) 2023 (western US) (ver. 2.0, February 2022)
This Data Release contains preliminary versions of two related databases: 1) A fault sections database ('NSHM23_FSD_v2'), which depicts the geometry of faults capable of hosting independent earthquakes, and 2) An earthquake geology site information database ('NSHM23_EQGeoDB_v2'), which contains fault slip-rate constraints at points. These databases were prepared in anticipation of updates to the N
Earthquake geology inputs for the U.S. National Seismic Hazard Model (NSHM) 2023, version 1.0
This Data Release contains preliminary versions of two related databases: 1) A fault sections database ("NSHM2023_FaultSections_v1"), which depicts the geometry of faults capable of hosting independent earthquakes, and 2) An earthquake geology site information database ("NSHM2023_EQGeoDB_v1"), which contains fault slip-rate constraints at points. These databases were prepared in anticipation of up
Filter Total Items: 42
Converted-wave reverse time migration imaging in subduction zone settings
We use a newly developed 2-D elastic reverse time migration (RTM) imaging algorithm based on the Helmholtz decomposition to test approaches for imaging the descending slab in subduction zone regions using local earthquake sources. Our elastic RTM method is designed to reconstruct incident and scattered wavefields at depth, isolate constituent P- and S-wave components via Helmholtz decomposition, a
Authors
Leah Langer, Fred Pollitz, Jeffrey McGuire
Slip deficit rates on southern Cascadia faults resolved with viscoelastic earthquake cycle modeling of geodetic deformation
The fore‐arc of the southern Cascadia subduction zone (CSZ), north of the Mendocino triple junction (MTJ), is home to a network of Quaternary‐active crustal faults that accumulate strain due to the interaction of the North American, Juan de Fuca (Gorda), and Pacific plates. These faults, including the Little Salmon and Mad River fault (LSF and MRF) zones, are located near the most populated parts
Authors
Kathryn Zerbe Materna, Jessica R. Murray, Fred Pollitz, Jason R. Patton
Solid Earth–atmosphere interaction forces during the 15 January 2022 Tonga eruption
Rapid venting of volcanic material during the 15 January 2022 Tonga eruption generated impulsive downward reaction forces on the Earth of ~2.0 × 1013 N that radiated seismic waves observed throughout the planet, with ~25 s source bursts persisting for ~4.5 hours. The force time history is determined by analysis of teleseismic P waves and Rayleigh waves with periods approximately <50 s, providing i
Authors
Ricardo Garza-Giron, Thorne Lay, Fred Pollitz, Hiroo Kanamori, Luis Rivera
Preface to the focus section on deformation models for the U.S. National Seismic Hazard Model
No abstract available.
Authors
Fred Pollitz, Alexandra Elise Hatem, Kaj M. Johnson
Western U.S. deformation models for the 2023 update to the U.S. National Seismic Hazard Model
This report describes geodetic and geologic information used to constrain deformation models of the 2023 update to the National Seismic Hazard Model (NSHM), a set of deformation models to interpret these data, and their implications for earthquake rates in the western United States. Recent updates provide a much larger data set of Global Positioning System crustal velocities than used in the 2014
Authors
Fred Pollitz, Eileen L. Evans, Edward H. Field, Alexandra Elise Hatem, Elizabeth H. Hearn, Kaj M Johnson, Jessica R. Murray, Peter M. Powers, Zheng-Kang Shen, Crystal Wespestad, Yuehua Zeng
Viscoelastic fault-based model of crustal deformation for the 2023 update to the U.S. National Seismic Hazard Model
The 2023 update to the National Seismic Hazard (NSHM) model is informed by several deformation models that furnish geodetically estimated fault slip rates. Here I describe a fault‐based model that permits estimation of long‐term slip rates on discrete faults and the distribution of off‐fault moment release. It is based on quantification of the earthquake cycle on a viscoelastic model of the seismo
Authors
Fred Pollitz
Exploring GPS observations of postseismic deformation following the 2012 MW7.8 Haida Gwaii and 2013 MW7.5 Craig, Alaska Earthquakes: Implications for viscoelastic Earth structure
The Queen Charlotte-Fairweather Fault (QC-FF) system off the coast of British Columbia and southeast Alaska is a highly active dextral strike-slip plate boundary that accommodates ∼50 mm/yr of relative motion between the Pacific and North America plates. Nine MW ≥ 6.7 earthquakes have occurred along the QC-FF system since 1910, including a MS(G-R)8.1 event in 1949. Two recent earthquakes, the Octo
Authors
Katherine A. Guns, Fred Pollitz, Thorne Lay, Han Yue
Kinematics of fault slip associated with the July 4-6 2019 Ridgecrest, Californai earthquakes sequence
The 2019 Ridgecrest, California, earthquake sequence produced observable crustal deformation over much of central and southern California, as well as surface rupture over several tens of kilometers. To obtain a detailed picture of the fault slip involved in the 4 July M 6.4 foreshock and 6 July M 7.1 mainshock, we combine strong‐motion seismic waveforms with crustal deformation observations to obt
Authors
Fred Pollitz, Jessica R. Murray, Jerry L. Svarc, Charles Wicks, Evelyn Roeloffs, Sarah E. Minson, Katherine Scharer, Katherine J. Kendrick, Kenneth W. Hudnut, Johanna Nevitt, Benjamin A. Brooks, David Mencin
Coseismic and post-seismic gravity disturbance induced by seismic sources using a 2.5-D spectral element method
I present a prescription for computing free-air coseismic and post-seismic gravity changes induced by seismic sources in a viscoelastic earth model. I assume a spherical earth geometry and a 2.5-D calculation, that is, 3-D motions that satisfy the equations of quasi-static equilibrium on a 2-D viscoelastic structure. The prescription permits application to regional gravity computations where a 2-D
Authors
Fred Pollitz
Coseismic slip and early afterslip of the M6.0 August 24, 2014 South Napa, California, earthquake
We employ strong motion seismograms and static offsets from the Global Positioning System, Interferometric Synthetic Aperture Radar, and other measurements in order to derive a coseismic slip and afterslip model of the M6.0 24 August 2014 South Napa earthquake. This earthquake ruptured an ∼13‐km‐long portion of the West Napa fault with predominantly right‐lateral strike slip. In the kinematic seis
Authors
Fred Pollitz, Jessica R. Murray, Sarah E. Minson, Charles W. Wicks, Jerry L. Svarc, Benjamin A. Brooks
Lithosphere and shallow asthenosphere rheology from observations of post-earthquake relaxation
In tectonically active regions, post-earthquake motions are generally shaped by a combination of continued fault slippage (afterslip) on a timescale of days to months and viscoelastic relaxation of the lower crust and upper mantle on a timescale of days to years. Transient crustal motions have been observed following numerous magnitude >~7 earthquakes in various tectonic settings: continental rift
Authors
Fred Pollitz
Induced seismicity reduces seismic hazard?
Earthquakes caused by human activities have been observed for decades. Often these are related to industrial activities pumping fluids into deep geologic formations, like with wastewater disposal. The simplest theory connecting these processes to earthquakes is straightforward: injection leads to fluid pressure changes that either reduce the strength of preexisting faults or generate new faults. I
Authors
Andrew J. Barbour, Fred Pollitz
STATIC1D
These programs solve the equations of static equilibrium in a spherically layered isotropic medium using a decomposition into spheroidal and toroidal motions.
Direct Green's Function Synthetic Seismograms
These programs are an implementation of the Direct Green’s Function method described by Friederich and Dalkolmo (1995) and Dalkolmo (1993).
VISCO1D
VISCO1D-v3 is a program package to calculate quasi-static deformation on a layered spherical Earth from a specified input source (fault plane parameters) at specified points on the surface or at depth.
Science and Products
- Data
Geodetic deformation model results and corrections for use in U.S. National Seismic Hazard Model 2023
This page houses model results used in the U.S. National Seismic Hazard Model, 2023. We include results from four geodetic deformation models (Pollitz, Zeng, Shen, Evans), post-seismic relaxation ("ghost transient") calculation (Hearn), and creep calculation (Johnson/Murray). Geologic deformation model results are available in Hatem et al. (2022a). An overview of all model procedures and comparisEarthquake geology inputs for the U.S. National Seismic Hazard Model (NSHM) 2023 (western US) (ver. 2.0, February 2022)
This Data Release contains preliminary versions of two related databases: 1) A fault sections database ('NSHM23_FSD_v2'), which depicts the geometry of faults capable of hosting independent earthquakes, and 2) An earthquake geology site information database ('NSHM23_EQGeoDB_v2'), which contains fault slip-rate constraints at points. These databases were prepared in anticipation of updates to the NEarthquake geology inputs for the U.S. National Seismic Hazard Model (NSHM) 2023, version 1.0
This Data Release contains preliminary versions of two related databases: 1) A fault sections database ("NSHM2023_FaultSections_v1"), which depicts the geometry of faults capable of hosting independent earthquakes, and 2) An earthquake geology site information database ("NSHM2023_EQGeoDB_v1"), which contains fault slip-rate constraints at points. These databases were prepared in anticipation of up - Publications
Filter Total Items: 42
Converted-wave reverse time migration imaging in subduction zone settings
We use a newly developed 2-D elastic reverse time migration (RTM) imaging algorithm based on the Helmholtz decomposition to test approaches for imaging the descending slab in subduction zone regions using local earthquake sources. Our elastic RTM method is designed to reconstruct incident and scattered wavefields at depth, isolate constituent P- and S-wave components via Helmholtz decomposition, aAuthorsLeah Langer, Fred Pollitz, Jeffrey McGuireSlip deficit rates on southern Cascadia faults resolved with viscoelastic earthquake cycle modeling of geodetic deformation
The fore‐arc of the southern Cascadia subduction zone (CSZ), north of the Mendocino triple junction (MTJ), is home to a network of Quaternary‐active crustal faults that accumulate strain due to the interaction of the North American, Juan de Fuca (Gorda), and Pacific plates. These faults, including the Little Salmon and Mad River fault (LSF and MRF) zones, are located near the most populated partsAuthorsKathryn Zerbe Materna, Jessica R. Murray, Fred Pollitz, Jason R. PattonSolid Earth–atmosphere interaction forces during the 15 January 2022 Tonga eruption
Rapid venting of volcanic material during the 15 January 2022 Tonga eruption generated impulsive downward reaction forces on the Earth of ~2.0 × 1013 N that radiated seismic waves observed throughout the planet, with ~25 s source bursts persisting for ~4.5 hours. The force time history is determined by analysis of teleseismic P waves and Rayleigh waves with periods approximately <50 s, providing iAuthorsRicardo Garza-Giron, Thorne Lay, Fred Pollitz, Hiroo Kanamori, Luis RiveraPreface to the focus section on deformation models for the U.S. National Seismic Hazard Model
No abstract available.AuthorsFred Pollitz, Alexandra Elise Hatem, Kaj M. JohnsonWestern U.S. deformation models for the 2023 update to the U.S. National Seismic Hazard Model
This report describes geodetic and geologic information used to constrain deformation models of the 2023 update to the National Seismic Hazard Model (NSHM), a set of deformation models to interpret these data, and their implications for earthquake rates in the western United States. Recent updates provide a much larger data set of Global Positioning System crustal velocities than used in the 2014AuthorsFred Pollitz, Eileen L. Evans, Edward H. Field, Alexandra Elise Hatem, Elizabeth H. Hearn, Kaj M Johnson, Jessica R. Murray, Peter M. Powers, Zheng-Kang Shen, Crystal Wespestad, Yuehua ZengViscoelastic fault-based model of crustal deformation for the 2023 update to the U.S. National Seismic Hazard Model
The 2023 update to the National Seismic Hazard (NSHM) model is informed by several deformation models that furnish geodetically estimated fault slip rates. Here I describe a fault‐based model that permits estimation of long‐term slip rates on discrete faults and the distribution of off‐fault moment release. It is based on quantification of the earthquake cycle on a viscoelastic model of the seismoAuthorsFred PollitzExploring GPS observations of postseismic deformation following the 2012 MW7.8 Haida Gwaii and 2013 MW7.5 Craig, Alaska Earthquakes: Implications for viscoelastic Earth structure
The Queen Charlotte-Fairweather Fault (QC-FF) system off the coast of British Columbia and southeast Alaska is a highly active dextral strike-slip plate boundary that accommodates ∼50 mm/yr of relative motion between the Pacific and North America plates. Nine MW ≥ 6.7 earthquakes have occurred along the QC-FF system since 1910, including a MS(G-R)8.1 event in 1949. Two recent earthquakes, the OctoAuthorsKatherine A. Guns, Fred Pollitz, Thorne Lay, Han YueKinematics of fault slip associated with the July 4-6 2019 Ridgecrest, Californai earthquakes sequence
The 2019 Ridgecrest, California, earthquake sequence produced observable crustal deformation over much of central and southern California, as well as surface rupture over several tens of kilometers. To obtain a detailed picture of the fault slip involved in the 4 July M 6.4 foreshock and 6 July M 7.1 mainshock, we combine strong‐motion seismic waveforms with crustal deformation observations to obtAuthorsFred Pollitz, Jessica R. Murray, Jerry L. Svarc, Charles Wicks, Evelyn Roeloffs, Sarah E. Minson, Katherine Scharer, Katherine J. Kendrick, Kenneth W. Hudnut, Johanna Nevitt, Benjamin A. Brooks, David MencinCoseismic and post-seismic gravity disturbance induced by seismic sources using a 2.5-D spectral element method
I present a prescription for computing free-air coseismic and post-seismic gravity changes induced by seismic sources in a viscoelastic earth model. I assume a spherical earth geometry and a 2.5-D calculation, that is, 3-D motions that satisfy the equations of quasi-static equilibrium on a 2-D viscoelastic structure. The prescription permits application to regional gravity computations where a 2-DAuthorsFred PollitzCoseismic slip and early afterslip of the M6.0 August 24, 2014 South Napa, California, earthquake
We employ strong motion seismograms and static offsets from the Global Positioning System, Interferometric Synthetic Aperture Radar, and other measurements in order to derive a coseismic slip and afterslip model of the M6.0 24 August 2014 South Napa earthquake. This earthquake ruptured an ∼13‐km‐long portion of the West Napa fault with predominantly right‐lateral strike slip. In the kinematic seisAuthorsFred Pollitz, Jessica R. Murray, Sarah E. Minson, Charles W. Wicks, Jerry L. Svarc, Benjamin A. BrooksLithosphere and shallow asthenosphere rheology from observations of post-earthquake relaxation
In tectonically active regions, post-earthquake motions are generally shaped by a combination of continued fault slippage (afterslip) on a timescale of days to months and viscoelastic relaxation of the lower crust and upper mantle on a timescale of days to years. Transient crustal motions have been observed following numerous magnitude >~7 earthquakes in various tectonic settings: continental riftAuthorsFred PollitzInduced seismicity reduces seismic hazard?
Earthquakes caused by human activities have been observed for decades. Often these are related to industrial activities pumping fluids into deep geologic formations, like with wastewater disposal. The simplest theory connecting these processes to earthquakes is straightforward: injection leads to fluid pressure changes that either reduce the strength of preexisting faults or generate new faults. IAuthorsAndrew J. Barbour, Fred Pollitz - Software
STATIC1D
These programs solve the equations of static equilibrium in a spherically layered isotropic medium using a decomposition into spheroidal and toroidal motions.
Direct Green's Function Synthetic Seismograms
These programs are an implementation of the Direct Green’s Function method described by Friederich and Dalkolmo (1995) and Dalkolmo (1993).
VISCO1D
VISCO1D-v3 is a program package to calculate quasi-static deformation on a layered spherical Earth from a specified input source (fault plane parameters) at specified points on the surface or at depth.